Both efforts seek to ensure that anxious Republican lawmakers -- many of whom have said they want to wait until September to assess President Bush's Iraq strategy -- get no break from the war over the summer.

'The debate on Iraq will continue,' House Speaker Nancy Pelosi (D-San Francisco) said last week. Pelosi, who in March helped push Democrats to embrace a withdrawal of American combat forces, has pledged that the House will vote on numerous measures aimed at ending the war.

Tom Matzzie, campaign manager for Americans Against Escalation in Iraq, the leading coalition against the war, promised an equally unpleasant summer for Republicans whenever they return home.

'Our job is to go into the congressional districts of members and create a political environment that is toxic,' he said. 'The public is there already. It is really about focusing their anger.'

In addition to pressuring Republicans, an aggressive legislative agenda also may be crucial for Democrats as they work to recover from party leaders' decision last month to abandon a withdrawal timeline.

Bush vetoed a war funding bill that included a specific date to begin pulling out U.S. forces, and he never wavered from his pledge to veto a second version of the bill if it contained any kind of timeline for withdrawal.

Many Democratic loyalists were infuriated when their party relented and passed a spending bill without timelines.

'To keep the faith, they are going to have to show that they are going to keep up the pressure,' said MoveOn.org Executive Director Eli Pariser, whose group has helped lead the grass-roots drive to end the war.

MoveOn.org and other liberal groups blasted Democratic lawmakers who backed the emergency war funding bill.

Republicans, who united with the White House to derail a withdrawal plan they called dangerously irresponsible, cheered the collapse of Democratic unity and continued to criticize withdrawal proposals.

'Signaling a date certain for withdrawal has never been a good policy,' said Ed Patru, a spokesman for the House Republican Conference. 'Republicans will oppose irresponsible Democrat policies.'

Many GOP lawmakers, including the leaders of the House and Senate, have signaled that they will be ready to reassess their support for the White House's Iraq strategy in September. The commander of U.S. forces in Iraq, Army Gen. David H. Petraeus, is expected to report that month on whether the troop buildup in Baghdad and Anbar province has reduced violence.

GOP unity, however, will be tested soon after lawmakers return this week from their Memorial Day recess.

Senate Democratic leaders are planning to consider new withdrawal proposals in just a few weeks, when the chamber begins debating the 2008 defense authorization bill, which outlines military spending priorities for the fiscal year beginning in October.

Senate Armed Services Committee Chairman Carl Levin (D-Mich.) said he planned to propose an amendment that would require the president to begin withdrawing U.S. forces within 120 days of the bill's enactment.

And Senate Majority Leader Harry Reid (D-Nev.), who has become one of the most ardent champions of bringing U.S. forces home, may revive a proposal by Sen. Russell D. Feingold (D-Wis.) to end funding for the war.

In the House, Pelosi has signaled her interest in considering legislation in the coming weeks to repeal the authorization for the war that Congress passed in 2002 -- a potentially powerful repudiation of the administration's war strategy.

'I believe it is appropriate that there be a national debate on the existing authorization for the war in Iraq and how that authorization has been affected by the events of the last four years,' Pelosi wrote in a May 24 letter to Rep. Ellen O. Tauscher (D-Alamo), a centrist sponsoring a deauthorization bill.

The legislation, Pelosi continued, 'provides a context for the consideration of the authorization issue and other issues like the redeployment of U.S. forces.'

By next month -- when Bush is required under the most recent war funding bill to give Congress a report on the Iraqi government's progress on a series of political benchmarks -- the House will probably be considering the 2008 defense appropriations bill. That could provide another vehicle for Democratic amendments calling for a withdrawal.

Senate consideration of that bill would follow.

By August, the Senate also may consider its own legislation to revoke authorization of the war, which is being championed by presidential hopeful Hillary Rodham Clinton (D-N.Y.), among others.

Democrats -- who are still working out the sequence of the summer's votes -- are wary of overplaying their hand, even with popular support for a congressionally mandated troop withdrawal.

'Votes for the sake of having votes doesn't really help us. What we need are votes that show we are gaining in strength. So we need to be thoughtful,' said Rep. Jim McGovern (D-Mass.), a leading war critic who sponsored legislation last month to mandate withdrawal by next spring.

'But it is incredibly important that the debate continue in June and July. It keeps the pressure on the White House, and it keeps the pressure on Republicans to break with the president,' he said. 'At a minimum, we need to be building ... for a showdown in September.'

While antiwar lawmakers push ahead, so too will the antiwar groups that have played an influential role in the national debate over Iraq.

Americans Against Escalation in Iraq, a coalition of organizations including MoveOn.org, VoteVets.org and the Service Employees International Union, plans to hire 80 people this summer to organize rallies and other protest activities aimed primarily at Republican lawmakers, Matzzie said.

The coalition also plans an aggressive television advertising campaign, particularly against Republicans who are up for reelection next year and seen as vulnerable, such as Sens. Susan Collins of Maine, John E. Sununu of New Hampshire and Norm Coleman of Minnesota.

'Our goal,' Matzzie said, 'is political extinction for war supporters.'