WASHINGTON -- While pressing President Bush all year to begin bringing troops home from Iraq, lawmakers leading the legislative campaign have not developed any plans to confront the widespread killing that could follow a pullout.
But many acknowledged that Iraq could first plunge into vicious sectarian fighting much like the kind of ethnic cleansing that consumed Bosnia a decade ago and is now afflicting Sudan's Darfur region. Yet they flatly rejected the use of U.S. troops to stop the killing.
"I wouldn't be surprised if it's horrendous," said House Appropriations Committee Chairman David R. Obey, a Wisconsin Democrat who has helped lead the drive against the war. "The only hope for the Iraqis is their own damned government, and there's slim hope for that."
Opponents of a withdrawal, including the president, have raised the specter of spiraling violence between Iraq's Shiites and Sunnis, a wider Middle Eastern war and a resurgent al-Qaida to blunt the accelerating Democratic effort to force the Bush administration to begin scaling back U.S. military involvement in Iraq. At the White House last week, Bush warned of "mass killings on a horrific scale."
The withdrawal measures offered by Democrats acknowledge that the U.S. will continue to play a military role in Iraq for years. The bills would allow an unspecified number of troops to remain to perform limited missions, such as training Iraqis and going after terrorist networks.
Most Democrats, including Senate Majority Leader Harry Reid of Nevada and House Speaker Nancy Pelosi of California, say such an approach, though not perfect, is the best of the bad options necessitated by the Bush administration's management of the war.
They argue that the presence of about 158,000 U.S. troops in Iraq is strengthening al-Qaida and giving Iraqi leaders a crutch that has allowed them to avoid reducing tensions between the country's sectarian communities.
"It's essential that we tell Iraq and the world that we are getting ready to leave ... both because the way to put pressure on Iraqi leaders is to let them know that the open-ended commitment is over and because the open-ended commitment plays into the hands of al-Qaida," said Sen. Carl Levin, a Michigan Democrat.
Many congressional Democrats also say that a U.S. withdrawal would encourage Iraq's neighbors, such as Iran and Syria, to play a more constructive role in resolving the conflict.
A few Democratic lawmakers, including Sen. Joseph R. Biden Jr., have proposals they hope would increase the likelihood of a stable outcome after a U.S. pull-back.
Biden advocates decentralizing the country into Kurdish, Sunni and Shiite regions.
But aside from broad calls for a diplomatic effort to work with Iraq's neighbors and more involvement by international organizations, most Democrats have no "Plan B," should a withdrawal yield chaos.
Senate Democrats' "New Direction" agenda, in which the party promotes its goals, does not address the issue of a post-withdrawal Iraq, noting only that "Senate Democrats remain committed to bring the war to a successful and responsible end."
House Democrats - who named the measure they passed last week the "Responsible Redeployment from Iraq Act" - also have not laid out a program for dealing with the aftermath.
The House withdrawal measure calls on the president to develop a new "comprehensive United States strategy for Iraq" that sets out more limited military missions and new "diplomatic initiatives to engage United States allies and others in the region to bring stability to Iraq."
The House asked for the strategy before Jan. 1, 2008.
The president has rejected any discussion of a redeployment until after Sept. 15, when the top U.S. commander in Iraq is to report on the success of the 30,000-troop buildup.
Few, if any, champions of pulling out U.S. forces are willing to intervene again, should ethnic and sectarian cleansing intensify.
"It will grow," predicted Oregon Sen. Gordon H. Smith, one of three Senate Republicans backing the Democratic withdrawal plan. "But it will burn itself out. That's how civil wars are fought. That's just the brutal truth."
Noam N. Levey writes for the Los Angeles Times.