WASHINGTON, Nov. 1 — A substantial majority of Americans expect Democrats to reduce or end American military involvement in Iraq if they win control of Congress next Tuesday, and say Republicans would maintain or increase troop levels to try to win the war if they hold on to power on Capitol Hill, according to the final New York Times/CBS News poll before the midterm election.

The poll found that just 29 percent of Americans approve of the way President Bush is managing the war in Iraq, matching the lowest mark of his presidency. Nearly 70 percent of Americans said Mr. Bush did not have a plan to end the war, and an overwhelming 80 percent said Mr. Bush’s latest effort to rally public support for the conflict amounted to a change in language but not policy.

The poll underlined the extent to which the war has framed the midterm elections. Americans cited Iraq as the most important issue affecting their vote, and majorities of Republicans and Democrats said they wanted a change in the government’s approach to the war. Only 20 percent said they thought the United States was winning in Iraq, down from a high of 36 percent in January.

Even beyond the war, the Times/CBS News poll, like most polls taken this fall, included worrisome indicators for Republicans as they go into the final days of a campaign in which many of them are bracing for a loss of seats in both the Houser and the Senate.

In a year when there are many close races, and where the parties’ success at turning out their voters could prove key, Democrats were more enthusiastic than Republicans about voting and more likely to say they would support their party’s candidates, though Republicans were slightly more likely to say they would turn out.

Fifty percent of independent voters, a closely watched segment of the electorate in such polarized times, said they intended to vote for the Democratic candidate, versus 23 percent who said they would vote for a Republican.

Among registered voters, 33 percent said they planned to support for Republicans, and 52 percent said they would vote for Democrats. As a rule, these kind of generic questions — while providing broad insights into the national mood — are often imprecise as a predictor of the outcome of hundreds of Congressional races, where local issues and personalities can shape the result.

Coming at the conclusion of a contentious midterm campaign, voters said that neither Democrats nor Republican had offered a plan for governing should they win on Tuesday, the poll found. Yet Americans have some clear notions of how government might change if Democrats win control of Congress: Beyond a quicker exit from Iraq, respondents said they thought a Democratic Congress would be more likely to increase the minimum wage, hold down rapidly rising health and prescription drugs costs, improve the economy and — as Republicans have said frequently in these closing days of the campaign — raise taxes.

By a slight margin, more respondents said the threat of terrorism would increase under Republicans than those who said it would increase under Democrats.

The nationwide telephone poll was conducted Friday through Tuesday with 1,084 adults, including 932 registered voters. The margin of sampling error for the entire sample is plus or minus three percentage points, and it is the same for registered voters.

Notwithstanding the clear expectation — among member of both parties Democrats and Republicans — that a Democratic Congress would produce a change in Iraqi policy, it is not clear how much influence they might have on Mr. Bush, who as commander in chief would retain the final say. In addition, while Democrats have coalesced around a general position of finding a way to reduce or end American involvement in Iraq, there is substantial disagreement among Democratic Congressional leaders and candidates about exactly how to accomplish this.

Nearly 75 percent of respondents — including 67 percent of Republicans and 92 percent of Democrats — said they expected Americans troops would be taken out of Iraq more swiftly under a Democratic Congress.

Forty-one percent of respondents said they expected troop levels in Iraq would decrease if Democrats win, while another 40 percent said the party would seek to remove all troops. Forty-one percent said they expected troop levels to remain the same if Republicans win, while 29 percent said they thought the United States would send more troops in if the Republicans continue to control Congress.

Those findings cut across party lines, but the poll found that Democrats were more likely to say Republicans would fortify American troop strength there, while Republicans were more likely to say Democrats would remove all troops.

Follow-up interviews with people questioned in the poll found clear expectations about the policies each party would pursue in Iraq, even if there was disagreement about which course is correct.

“If the Republicans continue in power, they would probably just want to keep doing what we’re doing and doing it longer and harder because the president is Republican and he’s the one who sent the troops there in the first place,” said Ashley Robertson, 20, a Democrat from Minnesota. “But right now I think it’s a bad thing to bring them all home because it’s like we went in there to try to help and we’re leaving them high and dry and saying, ‘clean up our mess.’ ”

Pat Atley, 73, a Republican from Florida, said she expected Republicans to press for more troops in Iraq if they stay in power — though she said she hoped they would not. “I’ve always felt we were never going to do any good over there,” she said, adding: “I don’t think we should increase our troops because increased troops aren’t going to do anything except put more of our men and women in jeopardy. “

Mr. Bush’s approval rating was 34 percent, unchanged from a poll three weeks ago, an anemic rating that explains why many Democrats are featuring him in their final advertisements, as well as why many Republican incumbents do not want him at their side. Fifty-six percent of respondents said Mr. Bush’s campaigning on behalf of candidates had generally hurt them, compared with 26 percent who said a campaign visit by Mr. Bush helped.

There was a slight increase, from 34 percent of respondents three weeks ago to 38 percent, who said they approved of how Mr. Bush was managing the economy. Similarly, there was a slight increase, from 40 percent in July to 44 percent now, in the number of respondents who said they approved of how Mr. Bush was managing the situation with North Korea.

In a year that has been marked by a series of Congressional corruption scandals, including some that have broken in the middle of this campaign, 58 percent of voters said that corruption was widespread in Washington; 35 percent said the Republican Party had the most number of corrupt politicians, compared with 15 percent who pointed to the Democratic Party.

In a campaign that will no doubt be remembered for the sheer volume of negative advertisements, voters were slightly more likely to put the blame on Republicans: 32 percent said they were responsible for negative campaigning this year, compared with 22 percent who blamed Democrats. Thirty-five percent said both parties were responsible.

The poll found the intensity of Democratic support for Democratic candidates is slightly greater than Republican support for Republican candidates, a finding that could give at least some solace to Democrats who have been concerned that the Republican Party’s formidable get out the vote operation would help them eke out victories in close Congressional races. Ninety percent of Democratic voters are planning to vote Democratic, while 83 percent of Republicans said they would support Republican candidates.

In addition, 50 percent of Democrats said they felt more enthusiastic about voting in this election than in previous ones, compared with 39 percent of Republicans. But 93 percent of Republicans said they were definitely or probably going to vote next Tuesday, compared with 89 percent of Democrats.