Washington ? John Kerry would change the situation. George W. Bush would change the world.

The electoral choice in 2004 is a stark and consequential one. These two candidates are night and day — more precisely, they are emotion vs. reason, instinct vs. intellect. A contest of innate spirits will animate and perhaps be decisive in their three televised debates.

Bush and Kerry project not only two Americas in their campaign speeches but two very different worlds that they would attempt to mold and lead. The course of the election and of U.S. foreign policy for the next four years rides on how uncommitted voters respond to the candidates’ emerging differences of approach and of essence.

Kerry’s slashing attack on Bush’s “stubborn incompetence” in the war in Iraq this week at New York University crystallized the choice that voters face in foreign policy. This is far more than an argument over tactics, as this election’s Third Man — Ralph Nader — claims.

The incumbent president is the radical in this unorthodox election year. In his view, a new threat to American security, in a new geographic region and from a new kind of enemy, demands a paradigm shift in international behavior that can be unilaterally enforced by American power if necessary.

Bush believes that America’s friends and foes abroad can — and must — be made to change their ways to make the world safer for democracies and particularly for the United States. Only by making the regimes of Saudi Arabia, Pakistan, Indonesia or Libya understand that their very survival is at stake can effective cooperation be gained in the war on al-Qaida and other parts of the loosely connected fanatical Islamist network.

The challenger is for once the pragmatist and traditionalist on foreign policy. Kerry first would change America’s approach to the world, then persuade and gently pressure allies and adversaries to return to established patterns of cooperation or coerced behavior.

Restoring NATO’s Cold War cohesion is a primary goal for Kerry, but a secondary tactical issue for Bush in grappling with turmoil in the Middle East, where European interests and reflexes often run counter to those of the United States. Israel is important to Kerry as a diplomatic and political partner; to Bush as a strategic ally in waging a long, necessary war.

These key differences are beginning to emerge clearly from an erratic, inconclusive campaign that has been fogged in by egregious personal bitterness and overwhelming media focus on two sideshows: controversy over service records from the Vietnam era and the periodic floundering of Kerry’s campaign apparatus. While most polls portray Bush as having an upper hand on national security, they also show him still vulnerable to events and to Kerry’s sharpening attacks on Iraq.

That is reason enough for caution and deeper deliberation by voters as well as pundits. It is also prudent to remember that campaigns produce their own dynamic of change as issues become more serious and contrasts more vivid. Other nations adapt in real time to what Kerry and Bush say (and are), and subtly change the policy environment the two leaders pretend to command.

This is particularly true for Kerry, whose repeated promises to get Europe to shoulder more of the burden in Iraq and in the war on terrorism have begun to worry even those Europeans who are favorably disposed to a change at the White House next January.

Gerhard Schroeder’s Germany is perhaps the most important example of a country that fully expects diplomatic tensions to continue if Bush is re-elected, but is also beginning to fret that a new crisis in NATO could emerge if a Kerry administration piles too many burdens on the alliance.

“I think some of my colleagues were perturbed by the briefings they heard at the Democratic convention in July about how much more Europe would have to do for President Kerry,” says one European diplomat. “All the speeches since then saying U.S. allies and not just Halliburton have to rebuild Iraq just add to the concern.”

Another future problem lies in the way in which Kerry and John Edwards have portrayed (although not named) Britain, Italy, Japan and other nations as having been bribed and coerced into serving in the coalition now in Iraq.

The fundamental task in foreign policy is to balance U.S. goals with U.S. capabilities. Failing thus far to make a convincing case that they know how to achieve this balance is one of the few things that Bush and Kerry have in common.