The choice

EARLIER THIS MONTH, two contenders for the 2008 Democratic presidential nomination stood together to stop what they saw as a dangerous drift in their party's stance on national security. At the National Press Club on May 9, Indiana Senator Evan Bayh summoned Democrats to dig in for ''what will in all likelihood be a generation-long struggle against jihadism and radical, suicidal terror." Former Virginia governor Mark Warner agreed that his partymates had to refute Karl Rove's taunt that they cling to a ''pre-9/11 worldview" by championing their own plans to fight al Qaeda. Though neither man named names, they implicitly chided their party's growing antiwar faction for railing against Bush's record without offering a vision of how to protect America.

The vision Bayh and Warner offered is one being heard increasingly from a host of younger journalists and policy mavens-from newly formed groups like the Truman National Security Project and the Foreign Policy Leadership Council to New Republic editor-at-large Peter Beinart, the author of a much-discussed new manifesto. It's an approach that repudiates the Democrats' post-Vietnam reluctance to use military power. Yet it also views armed force as part of an arsenal of tools-including economic development, robust alliances, and international law and institutions-that the US, as the world's de facto leader, must be ready to employ.

Such a vision would seem quite appealing, especially in a global age when there's no drawbridge for America to pull up. Yet no sooner had reports of Bayh and Warner's remarks appeared than they-and their way of thinking-came under fire from the bloggers and pundits whose influence among party activists they were seeking to curb. Across the Web, the politicians and their ilk were slammed as ''warmongers," ''Vichy Democrats," and ''enablers" of a Republican regime. And such attacks are nothing new. For months the left has been belittling the thinking of the internationalists, scoffing at how many of them backed Bush's invasion of Iraq, with The Nation-the flagship magazine of the antiwar faction-refusing to support any Democratic office-seeker who won't seek a speedy pullout.

Beneath this internecine party warfare lies a fundamental, and possibly debilitating, ideological divide. Liberals, who tend to view terrorism as the chief foreign policy concern, have been trying to revive the philosophy of internationalism-the belief that US intervention abroad can be noble in intent and beneficial in its results. Leftists, on the other hand, viewing the Iraq War as the most urgent problem, more often subscribe to a philosophy that might be called anti-imperialism-the belief that US intervention abroad is typically avaricious in intent and malign in its results.

By the end of his presidency, Bill Clinton had come to be a champion of intervention, and internationalists-such as former secretary of state Madeleine Albright, former UN ambassador Richard Holbrooke, Anne-Marie Slaughter of Princeton, and Lawrence Korb of the Center for American Progress-still dominated the Democratic party's foreign policy brain trust. But the anti-imperialist activists have conquered the blogosphere and, as the Iraq War drags on and hopes for a satisfying outcome fade, their arguments are winning converts among rank-and-file voters.

Consider: After Sept. 11, most Democrats agreed that defeating al Qaeda should be foreign policy goal No. 1. Now, while most Americans still share that goal, Democrats rate it 10th, according to a Security and Peace Initiative poll last year; withdrawal from Iraq is named first. Another survey, from MIT, showed that doubts about interventionism have spread beyond Iraq: As of November 2005, only 59 percent of the party-versus 94 percent of Republicans-still supported the invasion of Afghanistan.

The Democratic party's rift between liberal internationalists and radical anti-imperialists is, of course, decades old. And Beinart, in his deftly argued new book, ''The Good Fight: How Liberals-and Only Liberals-Can Win the War on Terror and Make America Great Again" (HarperCollins), helpfully grounds the current debate in its oft-forgotten history. A proud internationalist, Beinart persuasively shows that calls by today's liberals for America to actively project its power abroad represent not a betrayal of principle but a return to what liberalism is really all about.

The key moment to which Beinart hearkens is the dawn of the Cold War. In 1946 a divide over foreign affairs emerged on the left that presages today's. On one side President Truman and like-minded liberals saw in Josef Stalin's ambitions and barbarism a threat to Europe's freedom-and to America's world position. In contrast, leftists such as Commerce Secretary Henry A. Wallace favored a conciliatory stand toward the Soviet Union as a step toward peaceful coexistence. When Wallace publicly blasted the president's hard line that fall, Truman fired him.

For a while, it wasn't clear which man-or which philosophy-would prevail. With World War II having just ended, Americans weren't keen on a new global conflict. But a small band of anti-Communist liberals led by Eleanor Roosevelt and Hubert Humphrey stepped to the fore to provide ideological direction. In 1947, they transformed a faltering liberal-labor alliance known as the Union for Democratic Action into Americans for Democratic Action, proclaiming a ''two-front fight for democracy, both at home and abroad."

ADA believed that ''fellow traveling"-making common cause with American Communists and looking the other way at Stalin's crimes-would betray liberalism's core values and hinder its quest for reform. Two years later the historian Arthur Schlesinger Jr., one of ADA's leaders, distilled the group's philosophy in his now-classic book, ''The Vital Center," the title of which spoke to his belief in the inspirational power of freedom and democracy to combat totalitarianism.

The battle was joined. When in 1947 Truman proposed to help the governments of Greece and Turkey put down Communist insurgencies, Wallaceites called the move ''American imperialism"-but Democrats went along. Months later, Secretary of State George Marshall's sweeping plan to rebuild Europe again drew Wallace's scorn-but won support from the Democratic base. In the 1948 presidential campaign, Wallace challenged Truman and at first seemed poised to peel away liberal support. But, backed by ADA's intellectual and political firepower, Truman ended up winning the hearts, minds, and votes of most Democrats. For the next 15 years, the liberal internationalist outlook reigned.

Beinart is avowedly searching for a ''usable past," in Van Wyck Brooks's phrase, and for him the founding of ADA serves as a creation myth-a point of origin for the tradition he seeks to revive. In his telling, ADA's heroism in galvanizing Democrats behind a strong anti-Communist position-while also supporting civil rights, civil liberties, and an expansion of the New Deal-offers a model to internationalists today. Yet just when Beinart seems on the verge of lionizing ADA, he reckons squarely with their shortcomings. He raps Truman and Humphrey for failing to defend civil liberties at key moments during the Red Scare. And he censures Presidents Kennedy and Johnson for misapplying in Vietnam the containment doctrine that defined Cold War liberalism.

The Vietnam War, of course, wasn't a necessary outgrowth of liberal internationalism. Its sharpest critics included Cold War liberals such as diplomat George Kennan, political scientist Hans Morgenthau, and columnist Walter Lippmann. But over time the awful costs of the war, and its increasingly dubious goals, called the Democrats' foreign-policy principles into doubt.

Leading the interrogation were the radicals of the New Left. Even before Vietnam became a major issue, student radicals had been framing a critique of internationalism as a cover for imperialism-a drive to create open markets for US business. Many of these leftists held no love for Truman, Kennedy, Johnson, or liberalism itself. They saw scant difference between the parties, both of which they deemed hopelessly anti-Communist and pro-capitalist. For New Left radicals, Vietnam simply confirmed the bankruptcy of liberal internationalism that they had previously discerned.

As the war's futility became more apparent and liberals revolted against Johnson's refusal to reverse course, they joined with radicals in an uneasy alliance. As in today's Democratic party, in which liberals and leftists provisionally unite to oppose one or another of Bush's policies, the breadth of the antiwar movement concealed untenable contradictions. At bottom, the two camps rested their opposition to the war on totally different critiques. Liberals saw the war as a miscarriage of containment; radicals considered it an expression of American imperialism-with a minority fringe openly cheering on Ho Chi Minh. Beinart highlights as a telling moment the decision in 1965 by Students for a Democratic Society to delete the word ''totalitarian" from the description of the kinds of regimes it opposed-"a final break with the liberal tradition," he asserts.

If the ADA liberals won out in the battles of the 1940s, the outcome of the Democrats' internecine fighting in the 1960s was less clear-cut (although there was one undisputed winner: the Republicans). Most party regulars rejected the radical view of the war as a racist, imperialist campaign, and the violent tactics and extremist rhetoric on the fringes alienated more people than they seduced.

And yet the New Left did prevail in another, more subtle sense: By zeroing in on liberal internationalism's hubris-so ruinous in the case of Vietnam-they imbued Democrats of all stripes with a deep wariness of flexing American muscle overseas. Even ADA revised its views of America's proper place in the world. Indeed, the handful of liberals who didn't partake of this new wariness-such as former Humphrey aides Jeane Kirkpatrick and Ben Wattenberg-ceased to be liberals at all. They became neoconservatives.

If the early Cold War years provide today's liberals with a tradition that can inform and inspire a post-9/11 internationalism, the Vietnam War still reminds Democrats of the dangers of (to invoke a Vietnam-era phrase) the arrogance of power.

For many, including Beinart, Sept. 11 felt like the dawn of the Cold War-the curtain going up on a long, twilight struggle against a totalitarian foe. It helped revitalize internationalist ideas-which in any case Clinton, Albright, Holbrooke, and others had already begun to resuscitate in the 1990s. Democrats could give full-throated endorsement to the fight against al Qaeda, even while deploring Bush's disregard for differing viewpoints and disdain for international law.

The problem came in 2002, when Bush decided to invade Iraq. Suddenly-and prematurely, by the lights of Democratic internationalists, who were just getting their footing-the debate shifted. Now the question was whether to back a preventive war widely seen as illegitimate. Even before the American military set off for the Persian Gulf, skeptics were invoking the lessons of Vietnam-which pointed in exactly the opposite direction from those of the Cold War crises of the late '40s.

Since 2002, then, the Democrats' dilemma has been that the two main foreign policy issues, Iraq and terrorism, suggest different, if not opposite, remedies. Iraq, underscoring the perils of reckless military intervention, calls forth a fear of unintended consequences and recommends a policy of humility and restraint. In contrast, the continuing danger of terrorism by al Qaeda and kindred groups entails a policy of bold and at times aggressive involvement around the globe.

During the 2004 presidential campaign, John Kerry managed to heal this breach-or at least paper it over-by staking out a nuanced position of criticizing the war while emphasizing his eagerness to destroy al Qaeda. ''We are a nation at war-a global war on terror against an enemy unlike any we have ever known before," he fulminated in his acceptance speech. He was the cautious internationalist, the antiwar warrior. In the end, Kerry couldn't walk the tightrope, and after his loss, the old conflict within the party resumed.

Now, as the Iraq mess worsens, the dilemma becomes acute. Internationalism or anti-imperialism? Each worldview draws on different traditions, prescribes different policies, and envisions a different Democratic Party. Democrats face no more momentous choice than this in the months and years ahead.

David Greenberg is a professor of media studies and history at Rutgers University and author of ''Nixon's Shadow: The History of an Image."