When America is attacked, Americans respond. When America is not attacked but the president attacks people abroad, Americans support him--at least for a while. Political culture may help explain America's backing of presidents in wartime, but American political culture is increasingly divided and, if we are not attacked, that backing is increasingly ephemeral.

On September 11, 2001, my first reaction was that it was a replay of December 7, 1941. I recalled how the country reacted when Japan bombed Pearl Harbor; on 9/11 I saw many of the same reactions. I was trapped in a St. Louis hotel because air travel had been shut down, but everywhere in the city--a place Democrats ordinarily win at election time--there were signs of extraordinary patriotism. Though bus service there is managed by a government authority that is supposedly required to avoid any religious messages, the electronic screens on these vehicles that usually display the destination said "God Bless America." Flags were everywhere. And so it was all across the country.

Congress never voted to authorize the Executive Branch to overturn the Taliban regime; had it voted, it would have handed a lopsided victory to the President. Al-Qaeda had attacked us, and al-Qaeda was based in Afghanistan. That is all most Americans needed to know.

But when George H.W. Bush sought in January 1991 congressional approval to oust Iraq from Kuwait, the Senate passed the measure by a mere five votes. (The House passed it comfortably, but still with 183 representatives, including a majority of Democrats, voting against it.) When George W. Bush asked Congress to approve his invasion of Iraq in 2002, he got more support (296-183 in the House of Representatives, 77-23 in the Senate), but in both houses a majority of the Democratic Party opposed the venture.

The reluctance of congressional liberals to support both the 1991 and 2003 attacks on Iraq was not evident when President Clinton used military force against Serbs in Kosovo. There were no decisive congressional votes on these matters, but when the President ordered air strikes in Kosovo, he was warmly supported in speeches by liberal Democrats such as Paul Wellstone, David Bonior, Barbara Boxer and Carl Levin. He was opposed by conservative Republicans such as Don Nickles, John Warner, Dan Burton and Bob Barr. In the run up to the 2003 Iraq war, those same liberal Democrats opposed President George W. Bush, and the same conservative Republicans supported him. Partisanship no longer ends at the water's edge.

Of course, the attack on Kosovo and that on Iraq were different: The former relied on high-altitude air strikes, the latter on a ground invasion; and the U.S. combat victory over the Iraqi regime was decisive, while there was no decisive victory, only a desultory negotiation, in Kosovo. But above all there was the political difference: The military strike against Kosovo was waged by a Democratic president, that against Iraq by a Republican one.

Party has always made a difference. When Democratic presidents were in office, Democrats in the country were more supportive of our war effort in Vietnam than when a Republican was president. As soon as Richard Nixon took office in 1969, Democratic opposition to the war rose sharply, while Republican opposition remained unchanged.

American Enterprise Institute fellow Karlyn Bowman and I have studied support for America's past wars. We have concluded from a close analysis of public opinion poll data involving Korea, Vietnam and Iraq that about one-fifth of the country consists of a "peace party" that will object to virtually any use of American military power. When the country has been directly attacked, as was true on 9/11, public opposition to a military response has fallen to about one-tenth of the population. But when people were asked whether "a significant number of U.S. ground troops" should be sent to Afghanistan, opposition doubled. In short, one-fifth of the public will oppose any war effort that does not follow an immediate attack on this country and does not involve more than a handful of Special Operations forces. (For the whole story, see our essay in the Fall 2003 issue of The Public Interest.)

Of late, a significant fraction of the peace party is made up of African Americans, the great majority of whom opposed the 2003 invasion of Iraq. What is striking is that during the wars in Korea, Vietnam and Kuwait, black and white levels of support and opposition were roughly the same. We are not certain what has changed, but it may be that the antagonism of black voters to George W. Bush is part of the answer. Blacks backed Kennedy, Johnson and Clinton (all Democrats who took us to war), and blacks apparently accepted Republican George H.W. Bush's use of the military in Kuwait. But they have drawn the line at backing the military policy of the younger President Bush.

There is another characteristic of voters that correlates even more strongly with membership in the permanent peace party: advanced higher education. Having a postgraduate degree is the measurable feature that puts people most reliably into the peace camp. The peace party is made up of a disproportionate share of blacks and Democrats, but a majority of them do not always back peace. But a majority of people with postgraduate degrees are routinely in the peace party. For example, when one looks closely at people who supported Howard Dean in his antiwar primary campaign, well over half had postgraduate training or degrees, even though only about one-tenth of all Democrats (or all voters) have had such an exposure.

As a college professor, I would be the last to concede that what is taught in college--whether it is math, chemistry or politics--is learned and acted upon by students. If what they learn about calculus goes in one ear and out the other, what they learn about politics may follow the same general trans-cranial path. Indeed, the protests against the war in Iraq, unlike those against the war in Vietnam 30 to 40 years ago, tend to involve professors more than students. Teachers whom I know in various universities report few student demonstrators but many outraged professors. Nevertheless, something is passed along to college students that makes a difference. Just before the war in Iraq, about two-thirds of all Americans supported a war, but only about half of college graduates did.

No one is quite certain why this should be the case. Leftist graduate students in the 1960s became tenured professors in the 1990s, so perhaps what people learn in graduate school separates them from mainstream American culture. Or perhaps people who are already separated try to get a Ph.D. Whatever the reason, the professoriate is a considerable force not only because of its growing numbers (in 2001, 45,000 people got a Ph.D.), but because it teaches undergraduates, who, upon leaving college, make up about one-fourth of all adult Americans.

Leftist disdain for American foreign policy, except when it is pursued gently by a liberal president, is not the result of traditional liberal politics in America. Traditional liberalism has been generally rooted in a sense of compassion for the underprivileged and has been given its clearest expression by the labor and civil rights movements. These movements ordinarily recognized a boundary and an inspiration: for labor unions, the boundary was that of the United States, one that labor leaders were determined to defend against foreign enemies; for civil rights groups, the inspiration was a religious commitment to human moral equality that animated their desire to strike down social barriers to equal access.

Today the Left is dominated by neither labor nor civil rights groups, but by intellectuals. Intellectual Leftism is not based on personal experience or on religious belief but on cerebral abstractions. Those abstractions reflect generalizations about Society, Politics, Culture and the Economy (I capitalize the words to suggest their iconic significance). These generalizations tend to be simplifications about Who Really Runs Things, How Human Feelings Should Be Expressed, and Why the Conventional Wisdom Is Always Wrong.

Now, intellectual endeavor is certainly worthwhile. By the search for evidence, meaning and unknown facts, and through the exercise of relentless criticism and original thought, intellectuals can advance our knowledge of the world, improve our ability to find useful courses of action and strengthen our understanding of true happiness. But within the intellectual enterprise there lurk the seeds of its own perversion: We may search not simply for evidence but for righteousness; criticize behavior in ways that ignore profound human commitments to affection and patriotism; and over-generalize facts so that they condemn rather than explain other people.

Lionel Trilling made this clear in his famous argument about the cultivation of the adversarial and even subversive spirit of much modern thought that leads, as he put it, to "detaching the reader from the habits of thought and feeling that the culture imposes." Trilling coined the term "adversary culture" in 1946, but he could not have foreseen then how that culture would evolve. Today the nation is more deeply divided than at any time since the Administration of Franklin Roosevelt, and then the division could be largely explained by a clash of material interests. Now the split is about spirit and tolerance, one in which the stakes are not tax rates or government regulations but symbolic and moral questions of human purpose. The old American Liberty League might criticize Roosevelt while the labor unions defended him, but today MoveOn.org--a collection of "two million online activists"--asserts that it ought to control the Democratic Party. Rival groups of "online conservative activists" have sprung up, and the battle between the two groups is joined by the exchange of polarizing comments and media attacks.

The next president will face this badly splintered culture. If he or she must respond to foreign or terrorist enemies who threaten us without attacking us, the president's actions will be akin not to defeating Tojo's Japan or Hitler's Germany or anything else so vivid, but to coping with a nuclear-armed Iran or North Korea or a shadowy subversive movement in a friendly state. The stark fact is that we live in a unipolar world in which the sole great power is internally divided and possibly too (mis)educated for its own good. We may thus (one cannot be certain here) increasingly lack the capacity to maintain a reasonable world peace. (We should mark well that it is the maintenance of peace, and not its creation, about which we are speaking; since the collapse of the old U.S.-Soviet rivalry, there has been a sharp decline in the number of small wars.)

In the greater Middle East, in what the Left routinely denounces as a "war for oil" (which, of course, it never has been), our actions have brought at least a chance for democracy to a pair of once-tyrannical nations, aided Lebanon in thinking that it can once again govern itself, and made Libya and Syria pull back from some reckless ventures. Not bad; and one can be cautiously optimistic that more may be achieved, but only if this country is prepared to take risks on behalf of curbing dangerous regimes. There is no certainty that the next administration will be able to retain what Franklin D. Roosevelt, Harry S. Truman, John F. Kennedy, Ronald Reagan and George W. Bush brought to our management of world affairs. The first three presidents were helped by labor leaders; the last two were pilloried by leftist leaders. In this country, the labor movement among private firms continues to shrink and the leftist movement continues to grow in influence, if not in absolute numbers. It is not a happy prospect.