Should liberals be foreign-policy idealists? Suddenly, the question is everywhere. In his new book Power and the Idealists, TNR contributing editor Paul Berman argues that today's interventionists are the true heirs of the radical spirit of 1960s liberalism. In The Washington Post last month, Richard Cohen urged Democrats not to abandon idealism, writing that "Bush's soggy religiosity clearly should not be the basis of a foreign policy. But neither should a cold refusal to recognize the role that morality can play." And in the new issue of The American Prospect, Matthew Yglesias and Sam Rosenfeld argue for a modest liberal idealism--one that recognizes the Iraq war as a mistake but preserves a place for moral considerations in foreign affairs. "Liberalism," they write, "has always been an idealistic doctrine, and should continue to be. ... Acknowledging the limits of armed intervention does, however, entail a recognition that injustice exists in the world that is beyond America's capacity to remedy."

This is an important discussion--potentially a useful corrective to years of drift in liberal rhetoric on world affairs. Foreign-policy idealism ought to be a first principle of liberalism, but you wouldn't know it from the 2004 presidential primaries, in which so-called progressive Howard Dean spoke of the "relatively low cost" of leaving Saddam Hussein in power from 1991 to 2003; or the subsequent general election, in which John Kerry indulged an ugly brand of America-Firstism, denouncing Bush for "opening firehouses in Baghdad and shutting them in the United States of America"; or the left-wing embrace of Michael Moore's glib Fahrenheit 9/11, in which prewar Iraq is depicted as a sunny paradise rather than a totalitarian nightmare. Thanks to Dean, Kerry, Moore, and others, overtones of realism--a denial of America's moral responsibility in world affairs--have crept into liberal rhetoric. This is a fundamentally bad thing--for progressives, for Democrats, and for America. And it is good to see liberal writers resisting this trend by reaffirming the primacy of idealism in the Democratic worldview.

But one topic has been curiously absent from this discussion: Darfur. Of course, it's understandable that any consideration of foreign-policy idealism would begin with Iraq. But while Iraq is an appropriate starting point for a conversation about the future of liberal foreign policy, it is not an appropriate ending point. A reexamination of liberal foreign policy cannot consist merely of a discussion about what American foreign policy has done; it must also include a consideration of what has to be done--in Iraq, yes, but also elsewhere in the world. And anyone who calls himself a liberal ought to agree that something must be done about Darfur.

In fact, Darfur is a crystal-clear test of liberals' commitment to foreign-policy idealism. Compared to Iraq, it is a relatively uncomplicated test. The humanitarian rationale for overthrowing Saddam Hussein rested partially on the past and the future: His removal opened the way to justice for past slaughter and precluded the possibility of future slaughter. When it came to the present, the case grew more complex. On the one hand, Saddam's Iraq circa 2003 was a brutal place. On the other hand, no mass slaughter was taking place, and no mass slaughter was imminent. The situation of Iraq in 2003 should have been troubling to liberals, far more troubling than it was to most. But was it a genuine humanitarian emergency--one that justified the loss of tens of thousands of American and Iraqi lives, the creation of postwar chaos, the commitment of billions of U.S. dollars that could have been spent for other important humanitarian purposes? Those remain difficult questions, which is why liberals still disagree about the war today, and will continue to, and should.

Darfur, by contrast, presents none of these complexities. It is ahumanitarian emergency. A genocide is taking place; hundreds of thousands have died or have been displaced; and there is reason to believe that the slaughter will not end until Western troops forcibly stop it--or until the genocide's targets are all dead. In his new book on the subject, historian Gérard Prunier explains the slaughter's origins with reference to other enterprises undertaken by the current Sudanese government:

"The Southern war had been of genocidal proportions. The Nuba Mountains Jihad had been another quasi-genocide. Now Darfur was going to be yet another. In none of these cases did we have a Sudanese equivalent to the Wannsee Conference, with all the top brass of the regime sitting down at a table and cold-bloodedly deciding on the annihilation of a racial group. There was no need to. The decision-makers understood each other without having to plan and plot. They knew what they had, they knew what they stood to lose, and beyond their ceaseless political squabbles they largely felt of one mind... It was done, and the rest is now history."

TNR Online contributor Eric Reeves has laid out a compelling case on this website over the past few months that Khartoum's strategy has shifted during the last year: Its plan now is to finish the Darfur genocide via subtler means than the episode began. Having chased Darfuris from their homes, the government and its militia proxies hope to force the evacuation of humanitarian agencies by fomenting general chaos and insecurity in the region. With the humanitarian workers gone, the residents of Darfur--cut off from their livelihoods, ravaged by malnutrition and disease--will die, and the genocide will be complete. Only military forces can provide the security that would allow the humanitarian workers to stay. The African Union troops currently on the ground are not, by themselves, up to the job. The International Crisis Group estimates that 12,000 to 15,000 troops could secure Darfur if the Khartoum government cooperates; if it resists (which is likely) then the number of troops will have to be larger. Such intervention need not be unilateral; in fact, given that our armed forces are stretched thin in Iraq and Afghanistan, it should be multilateral. But whatever form the intervention takes, the calculus is stark: Either we put Western troops on the ground in Darfur or we concede the likelihood that the genocide will run its gruesome course.

Any fair reading of the principles behind foreign-policy idealism would require some kind of Western intervention in Darfur. That's because Darfur, unlike Iraq, is an extreme case. Idealism, like all worldviews, is a spectrum: An aggressive idealist might counsel action to overthrow a regime like Saddam's; a more cautious idealist might urge progress through diplomatic means. But because idealism at its core is a belief in the role of morality in foreign policy, and because there is no greater moral evil than ongoing genocide, it is simply impossible to conceive of an idealism that would not demand strong action--diplomatic and, if necessary, military--to end the Darfur slaughter. In fact, there is only one label for a worldview that counsels inaction and silence in the face of genocide: realism.

And yet how many Democratic presidential hopefuls, senators, or congressmen have cast Darfur as a central test of what would constitute a decent liberal foreign policy? Perhaps a better question is, have any? A quick look at the recent press releases of those Democratic senators most likely to run for president in 2008 makes clear that Darfur is not a foreign-policy priority. As for the pundits and thinkers: Richard Cohen, who clearly considers himself an idealist, has never mentioned Darfur in his Washington Post column. Yglesias and Rosenfeld, in their much talked about Prospect article, allude to Darfur only once: in order to ridicule TNR for "knee-jerk hawkishness" because we have urged, among other interventions, "action to halt genocide in Sudan." Then they protest, "We are not realists." I'm not so sure. If one claims to be a believer in the moral use of American power, and yet one can't advocate the use of American power in the most clear-cut and extreme of moral cases, then when, exactly, would one ever advocate intervention on moral grounds?

To be sure, President Bush and the Republicans currently hold most of the power in Washington. No one should let them off the hook regarding Darfur. History will assign them--along with leaders of the United Nations and other Western countries--the greatest culpability for allowing this genocide to take place on their watch. But the primary culpability of Bush does not erase entirely the culpability of other actors on the political stage; and so liberals, too, have a duty to propose action. This obligation cuts to the heart of the unfolding debate over what a liberal foreign policy should look like. A liberalism that cannot make genocide prevention a central plank of its foreign policy is not an idealistic brand of liberalism. Nor is it a liberalism that people of conscience will ever find particularly attractive.

All of which brings me to a proposal of sorts. Darfur presents, first and foremost, a foreign policy challenge that must be met by those in power—and soon. But it also presents a chance for liberals to clarify their worldview, for themselves and for the country they aspire to once again lead. Precisely because Darfur is an easy case, it should unite those liberals who favored the Iraq war and those who opposed it; those who consider themselves liberal hawks and liberal doves; those who supported Joe Lieberman in 2004 and those who preferred Dennis Kucinich. Anyone who considers himself a liberal idealist should know where to stand on Darfur, and what must be done. The only people left on the outside of this coalition will be the most hard-hearted of the liberal realists; and I'm not sure those people deserve to be called liberals anyway.

It is incumbent on President Bush to act in Darfur--to lead our Western allies in a multilateral effort to secure the area. But since he seems to have no intention of doing this, it has become incumbent upon the political opposition to shame him into action. So let the Democratic foreign-policy thinkers draw a clear distinction on this issue between what our party would do and what President Bush has done. Let them tell voters clearly that ours is a political philosophy of human empathy and moral strength. Let every Democrat who hopes to win the presidential nomination in 2008--from Hillary in the center to Feingold on the left--offer a plan to end the Darfur genocide as a clear indication of their idealistic credentials. And should one of them win the White House, and should it still be necessary, let that person act decisively to save the people of Darfur--not despite his or her liberal instincts, but because of them.

Richard Just is editor of TNR Online.