This is a worthwhile article looking analyzing the many weaknesses of the Bush Doctrine of preventive war: Why the Bush Doctrine Cannot Be Sustained by Robert Jervis Political Science Quarterly Fall 2005 (*.pdf file). He writes:
This does not mean that the United States is now firmly set on a new course [i.e., a permanent Bush Doctrine]. Indeed, I do not think that the Bush Doctrine can be sustained. Bush’s domestic support rests on the belief that he is making the United States safer, not on an endorsement of a wider transformationist agenda. Especially in the absence of a clear political victory in Iraq, support for assertive hegemony is limited at best. But if Bush is forced to retract, he will not revert to the sort of coalition building that Clinton favored. Of course there will be a new president elected in 2008, but even if he or she wanted to pick up where Clinton left off, this will not be possible. Although allies would meet the United States more than halfway in their relief that policy had changed, they would realize that the permanence of the new American policy could not be guaranteed. The familiar role of anarchy in limiting the ability of states to bind themselves has been highlighted by Bush’s behavior and will not be forgotten.
The United States and others, then, face a difficult task. The collapse of the Bush foreign policy will not leave clear ground on which to build: new policies and forms of cooperation will have to be jury-rigged above the rubble of the recent past. The Bush administration having asserted the right (and the duty) to maintain order and provide what it believes to be collective goods, an American retraction will be greeted with initial relief by many, but it is also likely to produce disorder, unpredictability, and opportunities for others. (my emphasis)
Jervis' point about the next president not being able to pick up where Clinton left off is a particularly important one. Clinton's post-Cold War policy involved the United States acting as a leader of the democratic nations in an increasingly interdependent world with a "globalized" economy. He was able to maintain an alliance like NATO, whose main purpose of defending against the Soviet Union had gone away.
But the strength of NATO and similar partnerships were based on a baseline commitment to the alliance shared by both major US parties. The Iraq War, and the Bush administration's arrogant unilateralism in pursuing it, has placed our relations with European democracies especially, but with others as well, on a very different basis. And not a better one.