Three months ago the Russian energy giant Gazprom forced Ukraine to pay sharply higher prices for natural gas. At the time, the story was portrayed as a political struggle for control in Kiev. But last week Gazprom announced it was tripling gas prices in Belarus, a country that is politically close to the Kremlin. Moldova has been forced to accept a doubling of prices over the next three to four years, and the other former Soviet republics are already paying market prices for Russian gas.

The truth is that these price increases are not political. Rather, they reflect worrisome economic and geological facts about Russian gas fields. The Kremlin is not simply trying to use Gazprom to reassert authority in Belarus, Ukraine or anywhere else. There are in fact deep problems with Gazprom -- problems created by its inefficient management and a looming decline in gas production.

Russia controls over a quarter of the world's gas reserves -- more than any other country. Most of the known Russian reserves (about 80 percent) are in west Siberia and concentrated in a handful of giant and super-giant gas fields. Since the early 1970s the rate of discovery for these new fields has been declining. Moreover, output from the country's mainstay super-giant fields is also steadily falling.

Huge investments are needed to replace this dwindling supply, and all the options for new production will prove costly and difficult. New fields in the far north and east of the country are distant from most of Russia's people and export markets, requiring wholly new transport systems such as pipelines. Moreover, most of these fields are found in extremely harsh environments where it is technically and financially difficult to operate.

Gazprom controls neither the capital nor the technology that will be needed. The state-controlled company is already deeply in debt and burdened by many expensive obligations, such as supplying Russia's population and friends with cheap gas. The company has to work with foreign partners.

So far Gazprom has been able to forestall crisis. Economic stagnation across the former Soviet Union and Eastern Europe since 1990 dampened gas demand. Russia, which had a surplus at the time, sharply increased its gas exports and made contractual commitments that will remain in force for many years.

But following the long stagnation, Russia's internal gas consumption is rising again as the economy expands. And new Russian policies to promote development of the country's eastern regions will, in the next few years, require large new commitments to supply gas to that region (along with spending on railroads, airports and other infrastructure).

Even when the Russian economy was in the doldrums the country was notable as a large gas consumer because of its extremely inefficient energy system. Today Russia is the world's second-largest gas user, after the United States, although its economy is only one-twentieth the size of the U.S. economy.

Electricity in Russia is produced for the most part by gas, but the country's gas-fired electric generators work at 33 percent efficiency on average, compared with 50 to 55 percent in Europe. More than 90 percent of residential and industrial gas consumers don't have meters. Gas is even cheaper than coal -- Russia is the only large country where that is true -- so incentives to switch to an abundant fuel are weak.

In recent years Russia has boosted gas supplies by squeezing Turkmenistan to sell gas to Russia at a deep discount. But Turkmen gas production is poised to decline, and Turkmenistan's gas industry is barely functional because the country's political environment is scary for long-term investors. Other Central Asian suppliers, notably Kazakhstan, are unlikely to be able to bridge the gap.

Caught between growing internal consumption of gas, continued inefficiency and mounting external obligations, Russia's gas industry faces a looming crisis. Given the country's vast resources, it seems that many producers could fill the void. But a series of policy decisions created two roadblocks that Gazprom has been happy to reinforce. One is the lack of access to the Gazprom-controlled pipeline network, which explains why few companies even bother to look for gas: They know they can't get what they find to market. The other barrier to investment is the low internal prices, which make gas production uneconomic except for companies that can sell their products outside.

Gazprom needs cash -- much more cash -- for investment. At the same time, it needs a strong incentive for former Soviet republics to cut their own very inefficient consumption.

Analysts have ignored the risk that Russia's supplies could fall short because they focus on Russia's vast gas resources and the new Western investors who are -- albeit cautiously -- entering into joint ventures with Gazprom. But those resources and ventures are for the long term, and the looming crisis of supply is unfolding now.

The gas shortage is likely to become most acute over the next few years. If there is an unusually cold winter in 2008, the year of Russia's presidential election, then Gazprom will face a politically unpleasant choice: whether to cut off internal customers (voters) or the Western customers who are the firm's main source of hard cash.

The writer is a research fellow at the Program on Energy and Sustainable Development at Stanford University. She is co-author of "Axis of Oil" and of a forthcoming comprehensive review of Russia's gas pipelines.

The fierce debate on immigration ignores a crucial reality -- what is happening to the United States is only one piece, although a big one, of a much larger global picture.

That hit me a couple of weeks ago when I was in Singapore. The Southeast Asian island nation has long been hailed as an economic model, the business capital for the entire region.

But it is an economy facing demographic peril. Its small population of 4 million is shrinking, thanks to a very low fertility rate. Prosperous Singaporean couples work hard, have fewer children and worry about how to take care of their aging parents. By 2050, Singapore will have a median age of over 52, one of the oldest in the world.

Singapore's answer is to import labor. A third of its workforce are migrants, from construction workers to maids. One out of seven households employs a domestic worker -- low-paid women mostly from neighboring Philippines and Indonesia.

Singapore tries to lure "talents'' -- highly skilled and affluent migrants -- to stay permanently. But the men hauling bricks and the maids washing laundry are in a separate class of temporary guest workers, with no chance to join Singaporean society. If a maid becomes pregnant, she is shipped out within seven days. Employers have to post bonds that must be paid should their servants break the rules and try to stay, putting them in the role of migrant police.

Problems of abuse of domestic workers, including physical and sexual violence and confinement, are serious enough to have prompted a report last December by Human Rights Watch.

Singapore's dependence on migrant labor and its guest-worker policy may be at the extreme end but it's very much on the global spectrum. Labor, like capital and goods before it, is part of a global market. The movement of people across borders in search of wages and work, most of it from developing countries to developed, is growing at a phenomenal pace.

The numbers are staggering. From 1980 to 2000, the number of migrants living in the developed world more than doubled from 48 million to 110 million. Migrants make up an average 12 percent of the workforce in high-income countries. About 4 million migrants cross borders illegally every year.

The demand for labor is driven in part by a demographic disaster -- the falling birth rates of developed countries. Almost all of those countries now have fertility rates that are well below 2.1, the level at which a population replaces itself. At the very low end are Hong Kong (0.94), Korea (1.22) and Singapore in Asia (1.24), along with much of Eastern Europe.

Low fertility means shrinking workforces and aging populations. Without migration, according to a recent study, Europe's population would have declined by 4.4 million from 1995 to 2000. Immigration accounted for 75 percent of U.S. population growth during the same period.

This movement of people cannot be stopped, certainly not by hundreds of miles of fences or even by tens of thousands of border guards. It is an issue that cries out for global cooperation, for common policies that cut across national boundaries. Already, we can benefit from looking at what has worked -- and not worked -- elsewhere.

A Global Commission on International Migration, formed in 2003 by the United Nations secretary-general, has taken an initial stab. Their report, issued last winter, supports the growth of guest-worker programs.

The Senate immigration bill now up for debate includes a provision for a guest-worker program. The bill is clearly preferable to the punitive and ineffective approach of the House version. But the Singapore experience -- and previous guest-worker programs like the German import of Turks -- should prompt second thoughts about going down this road.

One problem is that the guests don't leave. The United States has its own experience with this in the bracero program to import farmworkers, and more recently with the supposedly temporary H1-B visas used so extensively by the high-tech industry here in Silicon Valley.

Most troubling to me, these programs create an underclass of migrants who are never assimilated, as happened in Germany. It sets us on the Singapore road, encouraging inhumane policing mechanisms. And it is a gilded invitation to employers to depress the wages and incomes of American workers, and not just in the dirty jobs that are supposedly so hard to fill.

The United States has been rightfully proud of a tradition that treats all immigrants as citizens in the making. Rather than guest workers, isn't it more American to set realistic immigration quotas and enforce them fairly?

The Middle East seems to occupy all the attention of our foreign-policymakers these days. But there are other parts of this globe that are probably more important, and potentially no less dangerous.

One of these is the Taiwan Strait. That narrow passage of water separates China from Taiwan, in Chinese minds a renegade province that must eventually be returned to its control.

The Chinese communist leadership dreads the prospect that Taiwan's democratically elected government might make the island's de facto independence a legal reality. China's heated military buildup in recent years is largely focused on creating the muscle to intimidate Taiwan and to seize the island if that fails.

A war across the Taiwan Strait makes the American top-five list of security dangers. The U.S. commitment to defend Taiwan is ambiguous, but it is not hard to imagine us being drawn into a conflict. And a war in the strait could easily expand to include Japan.

That is why the mayor of Taipei, Taiwan's capital city, got such a rousing welcome last week in Washington. Ma Ying-Jeou, or Mayor Ma as he is popularly known, does not threaten to upset the apple cart of cross-strait relations by pushing Chinese buttons with talk of independence, as the Taiwanese government loves to do.

Sitting down with Ma for breakfast as he made his way home to Taiwan, I could see why he was received with open arms at senior levels of the Bush administration. Ma, the leader of the opposition Kuomintang (KMT) party, is the front-runner in polls to win the 2008 presidential elections. He is articulate, a Harvard Law School graduate with movie-star looks and a reassuring message for Americans.

"We support maintenance of the status quo, which is also U.S. policy,'' he told me.

A KMT-led government would not waver from the "Five Nos,'' a pledge made by President Chen Shui-bian not to take steps toward a declaration of independence. He offers in addition a program of ``Five Dos'' should it return to power.

First, the KMT hopes to resume negotiations with the mainland, based on a 1992 agreement that while there is one China, there are different interpretations of what that means. Second, it will try to reach a peace agreement, lasting from 30 to 50 years. Third, the KMT would expand the already massive economic ties between Taiwan and the mainland into a possible cross-strait common market. Fourth, the KMT would try to create a formula to allow Taiwan to participate in international affairs, including global organizations, short of being an independent state. Last, it would expand cross-strait cultural and education exchanges.

Ma downplays the threat from Beijing these days. "Their goal is no trouble,'' he told me. "They are not interested in unification right now.'' But, he said, the Chinese do worry about "the further drifting away of Taiwan.'' That drift, he fears, could inadvertently force a conflict that might drag in the United States.

That charge is aimed at the government in Taipei. And it is a concern shared by U.S. officials who are visibly unhappy these days with Chen. The warm reception for Ma was intended to send that message to Taipei -- and also to Beijing, ahead of the visit next month of Chinese leader Hu Jintao.

Reassuring as Ma's words may be, there are reasons to be cautious about his message and his prospects.

Taiwanese nationalism may rattle the status quo, but so does China's military buildup. As does the failure of Taiwan to adopt a significant U.S. defense package, offered five years ago, to counter that buildup. The KMT blames the current government for this impasse but the party, which now controls the legislature, has blocked passage of the budget.

Deepening economic ties with China are a market reality, as Taiwan's electronics industry shifts production to low-wage China. But ultimately that could make them another Hong Kong, a satellite of Beijing that must bend to its political will.

Taiwanese are deeply divided. The KMT, the party of mainlanders who fled to the island after the communist victory in 1949, ruled Taiwan for decades as the exiled government of China. But democracy, which came in the 1990s, brought to power native Taiwanese who want to preserve their separate identity.

Ma may prove to be a political leader who plays better in Washington than back home. But if Taiwanese embrace his vision of the status quo at the ballot box, all the better. Ultimately, his mandate must come from Taiwanese, not Americans.

In his State of the Union address in January, President Bush stressed the importance of improving math education. He proposed to "train 70,000 high school teachers to lead advanced placement courses in math and science, bring 30,000 math and science professionals to teach in classrooms, and give early help to students who struggle with math."

But where will these teachers come from? And will the training of teachers be sufficient to increase the number of students choosing math and science careers? And why does all this matter?

Because mathematics is the foundation of the natural sciences. It is no coincidence that Isaac Newton, the man who formulated the law of gravitational attraction that revolutionized our understanding of the universe, was also the man who popularized the calculus. And the natural sciences, however pure, are what give us airplanes, cable TV and the Internet.

In the 2003 Program for International Student Assessment, a test that measures math literacy, American 15-year-olds performed worse than their peers in 23 countries, as well as those in Hong Kong. It's not hard to see why. According to the National Council of Teachers of Mathematics, 40 percent of the nation's middle school math teachers do not have the equivalent of an undergraduate minor in math. The average starting salary of a teacher is only $30,000, whereas the average starting salary for a recent college graduate in computer science or engineering is $50,000.

Short of following the British, who have proposed paying experienced math teachers more than $100,000, with a guaranteed minimum of $70,000, where will we find a way to attract the thousands of teachers George Bush wants?

New York State initiated an innovative program to bring teachers from Jamaica for two or four years to teach in New York schools. Jamaica, a developing nation where one U.S. dollar equals 65 Jamaican dollars, is nonetheless a stable, English-speaking nation with an unbroken democratic tradition; it stands poised to beat the United States in establishing the world's first Institute for Mathematical Methods in Counterterrorism. When teachers for the New York program were recruited on the campus of the University of the West Indies, recruiters found more experienced math and science teachers than they ever dreamed they would.

But you can have all the teachers in the world and still not inspire kids to learn math. My friend Autumn e-mailed me about her nephew, Joshua: "He's upset because he's asked several of the math teachers why math is important or what are certain formulas used for -- there has to be a use, correct?"

Autumn told her nephew about my work in counterterrorism and for the television crime drama "Numb3rs." Autumn reported, "He's told his math teachers about you as well, and about the show 'Numb3rs.' He's informing them that through something called lattice theory you are managing to fight terrorists -- all with math."

Mathematics is art, and should be appreciated for its beauty, not simply for its utility. But we cannot expect 11 year-olds to cherish totally order-disconnected topological spaces as much as professional mathematicians do.

As I first proposed in January 2005, television shows like "Numb3rs" (or "Medium") -- where the main characters are mathematicians -- could work with the National Council of Teachers of Mathematics to show kids how math is really used; the council and Texas Instruments are now working together to use "Numb3rs" to promote math literacy in schools.

Another way to inspire kids is to relate mathematics to something they see every day. In order to excite students and draw funding to his school, school superintendent Ronald Ross of Roosevelt, N.Y., has begun looking into the idea of creating a curriculum involving math and counterterrorism. What kinds of topics would students learn?

The opening line of the Oscar-winning movie "A Beautiful Mind" is "Mathematicians won the war." During World War II, the mathematics underlying cryptography played an important role in military planning. Winston Churchill admired Alan Turing, the mathematician who had mastered the German codes, recognizing him as the man who had perhaps made the single greatest individual contribution to defeating Hitler.

At Los Alamos, the lab that built the atomic bomb, Cliff Joslyn uses lattice theory to mine data drawn from thousands of reports of terrorist-related activity to discover patterns and relationships that were previously in shadow.

Lattice theoretical methods developed at MIT tell us the probability that we have disabled a terrorist cell, based on how many men we have taken out and what rank they hold in the organization. Lauren McGough, a Massachusetts high school student, tested the accuracy of this model by getting her classmates to pretend they were terrorists, passing orders down a fictitious chain of command, essentially confirming what the theory predicts.

High school students could learn algebra, trigonometry, calculus and logic while also learning concrete applications involving homeland security. No longer would students yawn and ask, "What is math good for?" Beauty could defeat both terror and boredom.

Whatever you may think of the State of the Union address, when it comes to supporting math education, we should all see pi to pi. President Bush is correct when he says that mathematics education in America must improve if the United States is to stay economically competitive, but the stakes are much higher than that. During the Cold War, the United States would not have tolerated a military gap between itself and its adversaries. Yet today, with 61 percent of all U.S. doctorates in math going to foreigners (15 percent to Chinese), we readily accept a "math gap."

Dollar for dollar, the best defense against our adversaries' weapons of mass destruction may be our allies in the Americas, armed with weapons of math instruction.

Improving math education is not merely a smart idea. It is a matter of national security. Algebra is one revolutionary Islamic concept we cannot afford to neglect or ignore.

Before attacking Iraq in March 2003, the United States told the world that Saddam Hussein had reconstituted his nuclear weapons program in defiance of the United Nations. That claim, used to justify the war, was based on assessments provided by the United States intelligence community. But as everyone now knows, those assessments were wrong. So Jeffrey T. Richelson's history of American nuclear intelligence, including our attempts to learn about Iraq's nuclear program, could hardly be more timely.

In "Spying on the Bomb," Richelson, the author of several books on American intelligence, has brought together a huge amount of information about Washington's efforts to track the nuclear weapons projects of other countries. He examines the nuclear projects of Nazi Germany, the Soviet Union, China, France, Israel, India, South Africa, Taiwan, Libya, Pakistan, Iran and North Korea, as well as Iraq. Through interviews and declassified documents as well as secondary works, he sets out briefly what we currently know about those projects and compares that with assessments of the time.

This may sound like heavy going, but Richelson writes with admirable clarity. And along the way he has fascinating stories to tell: about plans to assassinate the German physicist Werner Heisenberg during World War II; about discussions in the Kennedy and Johnson administrations on the possibility of attacking Chinese nuclear installations; about Indian measures to evade the gaze of American reconnaissance satellites; and about the bureaucratic infighting over the estimates on Iraq.

The United States has put an enormous effort into gathering information about the nuclear projects of other countries. After World War II it equipped aircraft with special filters to pick up radioactive debris from nuclear tests for isotopic analysis. It created a network of stations around the world to register the seismic effects of nuclear explosions. Most important, in 1960 it began to launch reconnaissance satellites that could take detailed photographs of nuclear sites in the Soviet Union and China. Richelson occasionally speculates about the role of communications intercepts and of spies, but these appear from his account to have been much less important than the other methods of collecting information.

Through these means the United States has gathered a vast quantity of data, sometimes to surprising effect. Intelligence played a crucial role in the cold war, for instance, by reducing uncertainty about Soviet nuclear forces. Alongside such successes, however, there have been failures. One notable example concerned the first Soviet test, which took place in August 1949, much sooner than the C.I.A. had predicted. Another was the failure to detect Indian preparations for tests in May 1998, even though at an earlier time the United States, with the help of satellite intelligence, had managed to learn about preparations the Indians were making and to head off their tests.

But the most serious failure of all was in Iraq in 2003, because in no other case did the intelligence assessments serve as justification for the use of military force. The information needed for avoiding political surprise is one thing. That needed for preventive war is quite another, if only because of the consequences of making a mistake.

Beyond making the uncontroversial recommendation that "aggressive and inventive intelligence collection and analysis" should continue, Richelson draws no general conclusions. That is a pity, because his rich material points to issues that cry out for further analysis. He suggests in one or two cases that failures sprang from the mind-set of the intelligence community, but he does not elaborate on this point. He has little to say about relations between policy makers and the intelligence community, even though the quality of intelligence and the use made of it depend heavily on that relationship.

His focus is no less narrow in his discussion of foreign nuclear projects. He concentrates on the programs themselves, paying very little attention to their political context. Does that reflect a technological bias in nuclear intelligence? Would, for example, the prewar assessment of Iraqi nuclear capabilities have been more accurate if it had paid more attention to the broader political and economic circumstances of Hussein's regime?

The task of intelligence has become more complex than it was during the cold war. A single dominant nuclear opponent has now been replaced by a number of nuclear states, along with states and stateless terrorists that are aiming to get their hands on nuclear weapons. Meanwhile, the technology needed for producing nuclear weapons has become easier to acquire.

Many critics believe the recent performance of the intelligence community shows it has not responded adequately to this new situation. Richelson does not have much to say on this question; nor does he discuss the likely impact of the current reforms, initiated in response to the Iraq war, on the quality of intelligence. His reticence may imply that he does not think reform is necessary. Still, it is disappointing that he does not draw on his historical survey to discuss whether new approaches are needed for dealing with nuclear threats, and, if so, what those new approaches might be.

The nuclear deal reached during President Bush's recent visit to India unleashed a predictable wave of criticism. From editorial and op-ed pages to Congress, led by the left but supported on the right, the administration has been assailed for making a bad bargain.

Under the agreement, which still needs congressional approval, India would open much of its nuclear facilities to international inspections in return for gaining access to the world's supplies of uranium and U.S. nuclear expertise.

The attacks on the deal reflect the view of the nonproliferation lobby -- the experts and policymakers whose central concern is to stop the spread of nuclear weapons. I share their aim. But American arguments against the India deal are misleading and only expose the deep contradictions, if not hypocrisy, of our own nuclear policies.

There are two main criticisms of the agreement: first, it undermines the Nuclear Nonproliferation Treaty, the NPT, and second, it permits, even encourages, India to expand its nuclear weapons production.

The NPT issue is particularly sensitive at a time when the international community is trying to persuade Iran to give up certain nuclear technologies which many nations fear are part of a secret bomb program.

The NPT created two sets of global rules -- one for the five nuclear weapons powers it recognizes (China, the United States, Russia, Britain and France) and another for everyone else. The five, for example, allow only "voluntary'' international safeguards on their civilian nuclear facilities. They have no obligation to open their military programs to any kind of scrutiny. And the NPT places no real limits on their arsenals, other than a vague commitment to reduce and eventually eliminate all nuclear weapons.

The rest must open their nuclear energy programs fully to international inspection and agree never to build bombs. In exchange, they gain access to the peaceful uses of nuclear energy.

Iran -- and North Korea -- made that bargain and can be held to account for breaking the rules. But India consistently regarded that as an unequal trade-off and never signed the NPT; neither did Pakistan and Israel, two other nuclear weapons states.

India's nuclear program is the product of decades of largely indigenous effort; it did not result from secretive proliferation in violation of the NPT.

The deal with India turns the five into six. It treats India as a de facto member of the inner club. The deal would require changes in U.S. law to remove existing restrictions on the transfer of nuclear energy technology, changes that would allow India to be treated no differently from China.

That does not weaken the NPT -- it strengthens it. It brings it more into accord with reality and gives India a stake in a system it had previously rejected as unfair. It paves the way for India to join the Nuclear Suppliers Group, the international organization that controls nuclear exports.

The critics are right that the deal enables India to expand its production of fissile materials to make nuclear warheads. Eight of India's 22 power reactors will remain outside international controls, along with a new breeder reactor. The Indians fought for that exemption because they feel their nuclear arsenal may not be large enough to deter a nuclear first strike by Pakistan or China in the future. Critics fear that with increased access to uranium and limited inspections, India will set off an arms race in South Asia.

Again, the agreement simply treats India like the five. Nonproliferation experts claim that unlike India, however, the five have halted their production of plutonium and highly enriched uranium that could be used to build new weapons. This is true, but misleading.

The five have massive stockpiles of fissile material built up during the Cold War. "If I've got a full pantry, it's easy for me to swear off trips to the supermarket,'' said Michael Levi, an arms-control expert at the Council on Foreign Relations.

Moreover, the United States has embarked on a new program to rebuild its nuclear weapons production capability, including creating new facilities to produce plutonium cores for warheads and to assemble them.

India has agreed to back a global pact to cut off fissile-material production. But the Bush administration does not support a treaty that would actually verify this is taking place. And the U.S. Senate has refused to ratify the Comprehensive Test Ban Treaty that would permanently halt any new testing of nuclear weapons.

A Congress that can support those policies is hardly in a position to challenge the administration's agreement with India. Rather than block the U.S.-India deal, it makes more sense to improve it. This could include reaching agreements for cooperation between the two countries to ensure the safety and security of nuclear facilities, including those for military purposes, suggested Stanford Professor Scott D. Sagan, a leading expert on nuclear safety and nonproliferation. "Reducing the risk of terrorist theft of nuclear materials or weapons in India would also help protect the United States,'' argues Sagan.

Beyond that, the six acknowledged nuclear powers should begin to seriously fulfill their part of the NPT bargain -- to cap fissile-material production, to ban nuclear testing, and to eventually radically reduce stored arsenals of nuclear weapons and materials.

It is time to acknowledge that the international community's strategy on Zimbabwe has failed.

Robert G. Mugabe's regime has survived even as the economy deteriorates further (unemployment is above 70 percent, and gross domestic product will decline another 7 percent this year) and personal freedom suffers greater assaults (the recent "drive out the rubbish" campaign left 700,000 people homeless).

Indeed, with the opposition Movement for Democratic Change (MDC) on the verge of collapse - following a bitter fight over whether to boycott the recent Senate elections and after years of sustained government pressure - the regime has a stronger grasp on power than ever. Doddering though he may be, Mr. Mugabe, who recently turned 82, has foiled the pressure of the United States and Britain and the quiet diplomacy of his neighbors in southern Africa.

Predictions of imminent change still crop up in Western newspapers on the occasion of every new crisis in Zimbabwe. But these predictions have not come to bear, and they likely will not. So long as Mr. Mugabe reigns, his Zimbabwe African National Union-Patriotic Front (ZANU-PF) regime will survive.

The international community tried to change things. It embarked on a strategy of concerted economic and diplomatic pressure to weaken the Mugabe regime, trying to force it to either back down or submit to the democratic opposition. It's clear that strategy has failed.

It is, therefore, time to focus international attention on the prospect of Zimbabwe's only genuine political opening in the years ahead: the exit of Mr. Mugabe, whether through retirement or death, which will leave the regime internally and externally vulnerable.

Internally, the ZANU-PF regime without Mr. Mugabe at the helm will be uniquely susceptible in an election. In sub-Saharan Africa, opposition candidates have won post-transitional elections only 5 percent of the time against incumbents but 33 percent of the time against regimes' designated successors.

The most important reason for that is the incumbent's exit removes the regime's glue. The regime fractures into competing factions and is left with a substantially reduced capacity to repress the political opposition and rig an election.

In Kenya, after President Daniel T. arap Moi, and in Ghana, after President Jerry J. Rawlings, the regimes did not - could not - resort to all the dirty tactics that they certainly would have used had the incumbents run. In turn, these political openings have tended to galvanize the fractured opposition to successfully cooperate.

A ZANU-PF that is deeply unpopular, badly fractured among ethnic groups and between moderates and hard-liners (the expulsion of the information minister, Jonathan Moyo, is the beginning) and facing a reinvigorated opposition will not likely be able to effectively rig elections, let alone win the popular vote.

It will be critical, then, that presidential elections be held within a year of Mr. Mugabe's exit, before the regime has too much time to consolidate. If Mr. Mugabe's exit does not occur within that window before the 2008 elections, then international, and particularly regional, pressure will be crucial in forcing early elections.

Externally, Mr. Mugabe's exit may prompt genuine regional pressure. Analysts have long emphasized that international pressure requires the support of Zimbabwe's neighbors - especially South Africa - that have significant political and economic leverage. But to the great frustration of Western governments, southern African countries have thus far refused to publicly challenge Mr. Mugabe.

Their reluctance has much to do with Mr. Mugabe's status as a hero of Zimbabwe's anti-colonial struggle and a champion of liberation struggles elsewhere. Southern African nations will have much greater political room to apply real pressure on Zimbabwe when its leader lacks such credentials.

Simultaneously, the prospect of an altogether different level of violence might shake the complacency of southern African nations. Zimbabwe's implosion has not, thus far, been entirely bad for its neighbors. They have benefited from the elimination of economic competition and from the influx of professionals, and they have retained confidence that Mr. Mugabe can keep control.

But there is a real danger, if a post-Mugabe Zimbabwe is not handled adroitly, that elements of the opposition, disaffected war veterans and youth militia and losers in the ZANU-PF factional battle will take up arms and plunge Zimbabwe into civil war.

This specter should push neighboring countries to step up their efforts, especially to press the post-Mugabe regime to hold new presidential elections and encourage moderate elements within ZANU-PF.

Notwithstanding its occasional fulminations against Zimbabwe, the United States has failed in its efforts to unseat Mr. Mugabe's regime. The United States should focus now on his eventual exit by helping the MDC to overcome its bitter infighting and engaging Zimbabwe's neighbors, especially South Africa, in vigorous diplomacy, pushing them to prepare for the occasion.

The stakes could not be higher, for if the post-Mugabe period is the first genuine opportunity for political change in Zimbabwe, it may also be the last for some time.