Exchanging the heat of Baghdad for the swelter of Washington, Iraqi Prime Minister Nuri al-Maliki is in town to meet with President George W. Bush and address a joint session of Congress this July.

At a press conference with the president, Maliki criticizes Israel's airstrikes in Lebanon and calls for an immediate cease-fire, echoing the sentiment of the Iraqi parliament - which earlier in the week passed a resolution denouncing the Israeli campaign as "criminal aggression." Democratic National Committee Chairman Howard Dean wastes no time firing back, calling Maliki an "anti-Semite." Several Congressional Democrats demand that Maliki's upcoming address to Congress be canceled unless he retracts his statement and apologizes.

Across town, Peter Beinart sits in his office, dismayed. He views the Democrats purportedly principled stand against Maliki as little more than short-sighted, self-destructive political machinations. He wonders: How will Maliki establish credibility with his majority Shi'ite-Arab country if Democrats insist on making him look like an American puppet? And without that credibility his government will fail, and America desperately needs him to succeed. Beinart vents his frustration in an acerbic opinion column that will appear by week's end in The Washington Post.

"It was about appearing more pro-Israel than the White House and thus pandering to Jewish voters," Beinart writes. "It's jingoism with a liberal face."

But Peter Beinart is no bomb-throwing conservative bloviator. Rather, he was until earlier this year the editor of The New Republic, the venerable liberal opinion journal. He now holds the position of editor-at-large, and he has just published his first book, The Good Fight: Why Liberals - and Only Liberals - Can Win the War on Terror and Make America Great Again, in which he articulates a muscularly liberal vision of America's role in the world. It has sparked heated debate within a Democratic Party that has long struggled to find its voice on national security.

The time is right for the undertaking. Less than two years ago, George W. Bush delivered an exceptionally idealistic inaugural address that focused almost exclusively on America's role in the world. "All who live in tyranny and hopelessness can know: the United States will not ignore your oppression, or excuse your oppressors," Bush declared. "When you stand for your liberty, we will stand with you."

But now - with Iraq in bloody tatters, Afghanistan backsliding into warfare, confrontation with Iran, and Israelis and Lebanese recently confined to bomb shelters democracy, democracy promotion, and humanitarian intervention have become dirty words in the American political lexicon. Americans are now weary of grand visions. There is no longer much appetite for Bush's brand of democratic evangelism. Disillusioned Americans are turning inward.

Beinart worries that the view of what he calls the "anti-imperialist Left" - those for whom the fundamental issue is American imperialism - is gaining ground.

He cites a May 2005 Pew Research Center study of the American electorate in which it found that "Foreign affairs assertiveness now almost completely distinguishes Republicanoriented voters from the Democratic-oriented voters." Another poll showed that while conservatives, and Americans in general, cited destroying al-Qaida as their top foreign policy priority, among liberals it tied for 10th.

This trend was underscored by a November 2005 M.I.T. survey, which found that only 59 percent of Democrats - as opposed to 94% of Republicans - still approved of America's decision to invade Afghanistan. And only 57% of Democrats - as opposed to 95% of Republicans - supported using US troops "to destroy a terrorist camp."

"Many liberals," Beinart writes, "simply no longer see the war on terror as their fight."

And for a liberal internationalist like Beinart - who believes America has a moral purpose at home and in the world - this is profoundly disheartening. After all, if liberals believe every step America takes abroad is the first step towards quagmire it is impossible to take any step at all. And in the age of jihad, how can such a timid ideology rally America to its own defense?

"I THINK there is a danger of over-learning the lessons of Iraq in the same way that some liberals over-learned the lessons of Vietnam," Beinart says from behind his bare and scuffed wooden desk.

The first thing you notice about Beinart is his youth. It is as though every physical attribute conspires to make him appear even younger than his 35 years. Beinart's office at The New Republicis Spartan and modest. His only effort at interior decoration is a small photograph of his nine-month-old son, Ezra, perched on top of his dusty computer monitor. A somewhat-disheveled bookshelf lines one wall.

Beinart was an early and vocal proponent of the Iraq war, one of the so-called "liberal hawks," who was convinced that military action was the only way to prevent Saddam Hussein from obtaining a nuclear bomb. In addition, he was moved by the compelling humanitarian case for overthrowing the Ba'athist regime.

For this small contingent of leftist intellectuals, a series of altruistic American interventions in Bosnia, Haiti and Kosovo throughout the Nineties birthed a shift in thinking about American military power. As the writer Paul Berman reflected at the time: "We who used to be the party of anti-intervention (because we were anti-imperialists) should now become, in the case of various dictators and genocidal situations, the party of intervention (because we are democrats)."

"I was wrong," Beinart writes at the very beginning of The Good Fight. "I could not imagine that Saddam Hussein, given his record, had abandoned his nuclear program... And I could not imagine that the Bush administration would so utterly fail to plan for the war's aftermath, given that they had so much riding on its success."

But Beinart goes beyond merely faulting the incompetent execution of the postwar. Rather, he has come to the conclusion that the war was wrong "in theory."