ASERIOUS congressional debate about Iraq is essential at a time when public support for the mission is falling and the danger of failure seems great. Aggressive challenges to the Bush administration's military and political strategy -- even calls for an immediate withdrawal of troops, such as that made by Rep. John P. Murtha (D-Pa.) on Thursday -- must be part of that democratic discussion. Yet what we've mainly seen during the past two weeks is a shameful exercise in demagoguery and name-calling.

Democrats accuse President Bush of deliberately lying about the grounds for war three years ago. Vice President Cheney responds by calling accusations by the Democrats "dishonest and reprehensible, " while Mr. Bush claims his critics "send mixed signals to our troops and the enemy." Mr. Murtha, a 73-year-old former Marine, was said by the White House to advocate "surrender to the terrorists" and called a coward by Republican members of Congress. He replied by smearing Mr. Cheney and Mr. Bush as "guys who got five deferments and never been there, and send people to war."

It sounds like the final days of a bitter, mud-slinging political campaign. But what is at stake is not an election but a war in which American soldiers are being killed and wounded almost every day and in which one possible outcome is a major victory for the Islamic extremist movement that carried out the attacks of Sept. 11, 2001. Those losses won't be stemmed, nor the dangers averted, by attack rhetoric or sound bites that deliberately distort the facts. Leaders of both parties know that, of course. Which raises the question: Is their priority to win in Iraq -- or in next year's midterm elections?

The hard truth is that those two objectives may be in conflict. The war is unpopular for many reasons, including the painful human losses, the failure to find weapons of mass destruction, incompetent management of postwar reconstruction and the involvement of some U.S. personnel in appalling practices of torture. Mr. Murtha, deeply moved by the wounded soldiers he has visited, cited several other serious problems, including the wear and tear on the U.S. military and the steady increase in attacks by insurgents.

Yet Mr. Murtha, like other Democrats who advocate an early pullout, grossly misstates the nature of the conflict in Iraq. In a news conference, he contended that U.S. troops "have become the primary target" and have united Iraqis against them. In fact, far more Iraqis than Americans are being killed by the insurgents; Iraq is divided between a Shiite and Kurdish majority -- whose leaders strongly support a continued U.S. presence -- and a Sunni and Islamic extremist minority that seeks to drive international forces out so that it can try to impose a dictatorship on the rest of the country. As Democrats such as Sens. Joseph R. Biden Jr. (Del.) and Joseph I. Lieberman (Conn.) have recognized, a premature American departure from Iraq would not end but greatly escalate what is now a low-grade civil war. It could allow al Qaeda to claim a triumph and establish a base for attacking the United States and its allies in the Middle East.

Mr. Bush indulges in his own surreal rhetoric, insistently describing Iraq as a Manichaean battle between foreign terrorists and Iraqi democrats, rather than the multi-sided power struggle that it is. In so doing, he hamstrings his own diplomats and generals, who are trying to forge a political accord among the various Iraqi communities and isolate the foreign and Sunni extremists through a conventional counterinsurgency campaign. Many Democrats have no better alternative strategy, which may be why their leaders spend most of their time making charges about what was said, or not, about weapons of mass destruction in 2002.

What's needed is more talk about Iraq in 2005. Though there have been successes -- including the staging of an election and a constitutional referendum -- the country is in danger of splitting into pieces, and the Bush administration has not done enough to head that threat off. New elections in December could propel the country toward a political accord that would undermine the insurgency. But reconstruction has foundered and needs to be relaunched, with emphasis on supplying electricity and jobs. Iraqi troops are improving but still are far from ready to fight the counterinsurgency war on their own. If there is to be any chance of that war being won, the United States will have to commit its own forces to the fight for years, though perhaps not at current levels. The alternative is to risk a defeat that would be devastating to U.S. security. That's a hard truth to face: It can't be done amid a partisan free-for-all.