North Korea likes Senator John Kerry. Radio Pyongyang broadcasts the Democratic presidential candidate's speeches along with the regime's predictable denunciations of U.S. President George W. Bush. And the North Koreans are hardly alone. Opinion polls across the globe reflect deep discontent with the current White House occupant. After all, statements such as “working with other countries in the War on Terror is something we do for our sake—not theirs” are bound to irritate citizens and leaders of other nations. By contrast, non-Americans are likely more at ease with a U.S. leader who says “I believe in the international institutions and alliances that America helped to form and helps to lead.”

But be careful what you wish for. The first assertion is Kerry's, and the second comes from Bush. Although such statements may not accurately represent Kerry and Bush's natural proclivities, they may reveal more about the foreign policy of the next U.S. administration than any position paper intended to underscore the candidates' differences. Indeed, these comments by Kerry and Bush highlight a paradox that the candidates and U.S. voters alike are reluctant to recognize: If reelected, Bush will have difficulty sustaining the foreign policies of his first term, whereas a first-term Kerry presidency is bound to emulate some of Bush's more aggressive positions.

Imagine if Bush wins in November. In a second term, the president would discover that large-scale preemptive wars of choice are no longer an option. Despite major increases in military spending during Bush's first term, the U.S. military now finds itself seriously overstretched in terms of troops, funding, and operational capabilities. And if anyone thinks that recruiting foreign allies for the Iraq invasion in 2003 was difficult, doing so in support of another preemptive war would be close to impossible. Of course, if the American people are directly attacked or unambiguously provoked by a clearly identifiable enemy, the United States would retaliate forcefully. But the failure to find weapons of mass destruction in Iraq and the problematic postwar occupation have eroded domestic political support for any military adventures that cannot be unequivocally justified. The bar for significant U.S. military action abroad is now substantially higher than it was following the terrorist attacks of September 11, 2001.

In a second term, Bush is also likely to try harder to collaborate with Europe and the United Nations, especially on security matters. He has already been forced in that direction in the hope of reducing U.S. exposure to the postwar difficulties in Iraq. Indeed, Iraq's reconstruction will sooner or later require a larger U.N. presence, which will in turn require a more collaborative relationship with Europe. Also, Bush's “Greater Middle East Initiative” (to be announced formally at the Group of Eight meeting in June) aims to promote democracy in the region and exemplifies the president's increased disposition to build international coalitions. This effort stands in sharp contrast to the policy of unilateral disengagement from the Israeli-Palestinian conflict that Bush adopted at the beginning of his presidency. Thus, although the Bush administration's vaunted aversion to what then U.S. President Thomas Jefferson called “entangling alliances” may not disappear in a second term, Bush's rejection of multilateral action will be far less rigid and ideologically driven than it was during the first four years.

Now consider Kerry. If the Democrats recapture the White House, Kerry would quickly learn that some of his multilateral instincts are difficult to transform into sustainable policies. Some dictator, somewhere, may be emboldened to behave in ways that test the new president's mettle, thus compelling Kerry to act forcefully and unilaterally to show that neither he nor the United States has abdicated the use of force. And if the United Nations proves unwilling or unable to bail the United States out of Iraq, the Kerry administration would find itself obliged to unilaterally expand direct U.S. involvement there far beyond what it would prefer—and far beyond the current involvement under Bush. Whereas bitter security disputes with Europe have characterized Bush's presidency, protectionism and nasty trans-Atlantic trade clashes fueled by a weak U.S. dollar could instead become the hallmarks of a Kerry presidency. Kerry might also discover that Bush was correct in dismissing Europe's enthusiasm for multilateralism as mostly rhetorical and in believing that the European Union lacks the will, the power, and the money to act as a reliable ally in international emergencies.

All recent U.S. presidents have learned the hard way that, despite their immense power, they remain at the mercy of uncontrollable global forces that render their personal views and campaign promises largely irrelevant. Former U.S. President Bill Clinton's famous campaign dictum, “It's the economy, stupid,” proved better as a campaign slogan than as a predictor of how often international turmoil would pull his attention away from domestic issues. Bush reneged nearly as quickly on his campaign promise to adopt a humble foreign policy, wary of active foreign engagements and nation-building efforts.

Against this backdrop, Kerry's foreign admirers would do well to assume that, despite his best intentions, the senator might be unable to deliver on his commitment to a “bold, progressive internationalism.” By the same token, Bush's supporters at home would be well advised to realize that, if reelected, Bush will adopt some policies that will break their hearts—and probably his.