WASHINGTON — Peace in Iraq is proving more politically dangerous for President Bush than war.

The swiftly decided military conflict boosted Bush's standing in polls and strengthened his reelection prospects. But the unsettled postwar situation looms as a potential long-term political threat for the president, some analysts believe.

So far, rising public concern about the steady procession of U.S. casualties from guerrilla attacks in Iraq has not eroded support for the effort to rebuild the country. Two national surveys released this week suggested the same bottom line: Because most Americans believe that removing Iraqi President Saddam Hussein from power was important to U.S. security, they are willing to accept an extended reconstruction, even if that means the loss of some U.S. troops.

But opinion about the war in Iraq and its aftermath now appears far more fluid and complex than during the fighting. The percentage of polled Americans who say the rebuilding effort is going well is declining — as is the percentage who say the threat posed by Iraq justified the war.

And some experts believe that public opinion could tip against staying in Iraq if it appears that ordinary Iraqis are rejecting the U.S. presence and the mission is foundering.

That risk could be compounded if no conclusive evidence is found that Hussein was developing weapons of mass destruction.

"If weapons of mass destruction are found, that will solidify support, no matter how badly things go in the reconstruction," predicted Steven Kull, director of the Program on International Policy Attitudes at the University of Maryland.

But he added that if skepticism grows about the existence of banned weapons and American deaths continue, "those things could converge in a way that could ultimately become a negative for the president."

In a sign of shifting attitudes toward Bush's handling of postwar Iraq, some Democrats are reprising the charge they made before the war: that the president has been too reluctant to work with other nations.

"We need to stop trying to do everything by ourselves and internationalize the reconstruction of Iraq," said Will Marshall, president of the Progressive Policy Institute, a centrist Democratic think tank.

Democratic presidential candidates who backed the war also are becoming more pointed in their critiques.

Rep. Richard A. Gephardt of Missouri on Wednesday criticized comments that Bush made earlier in the day about the sporadic violence in postwar Iraq.

Bush said resistance forces hostile to the U.S. presence "feel like ... the conditions are such that they can attack us there. My answer is, bring them on."

In a statement, Gephardt said: "I have a message for the president: Enough of the phony, macho rhetoric. We should be focused on a long-term security plan that reduces the danger to our military personnel there.... We need a serious attempt to develop a postwar plan for Iraq and not more shoot-from-the-hip one-liners."

Sen. Joseph I. Lieberman of Connecticut, another war supporter among the Democratic candidates, is completing a commentary article accusing Bush of mishandling the reconstruction by delaying the transition to an Iraqi interim government and failing to give allies a large enough role in the process.

Bush declared the end of major combat operations in Iraq in a speech he gave aboard the aircraft carrier Abraham Lincoln on May 1. Since then, 66 American soldiers have died in Iraq, either in combat or accidents, according to the Pentagon. The war claimed 138 U.S. lives.

Richard Betts, director of Columbia University's Institute of War and Peace Studies, said the American public is likely to tolerate current casualty levels as long as the occupation is seen to be making progress.

But he added: "If we reach a point where more people die since Bush landed on the aircraft carrier than had died before, there will be more of an inclination to say, 'Quagmire.' "

A poll released Tuesday by Kull's group at the University of Maryland found that a majority of Americans — 53% — believed the rebuilding process was not going well.