Democrats are commanding a major lead going into the final weeks of the U.S. midterm-election campaigns, with support eroding for Republicans on the war in Iraq and ethics, a flurry of new polls are showing.

With about four weeks left before voters cast their ballots, polls are indicating that Americans are increasingly alienated from U.S. President George Bush and Congress, which could give Democrats a genuine chance of ending the Republicans' hold of Congress.

Democrats must pick up 15 House seats and six Senate seats to reclaim control of Congress.

A USA Today/Gallup poll gave Democrats a 23-point edge on Republicans in the congressional horse race, while a CNN poll gave Democrats a 21-point lead.

An ABC News/Washington Post poll found Democrats held a 54-41 per cent lead in the battle for Congress among registered and likely voters, which ABC reported was the biggest Democratic head start this close to Election Day in more than 20 years.

Meanwhile, a new CBS News/New York Times poll showed 79 per cent of respondents thought Republican leaders were more concerned about their political standing than about the safety of the teenage congressional assistants who may have received suggestive messages from disgraced former Florida Rep. Mark Foley.

Republicans, who have been scrambling to present a united front after details emerged about Foley's questionable behaviour toward the teenaged pages, are trying to keep the scandal from sinking their chances on November 7.

Observers say the fallout from details emerging about Foley and the teenaged pages has the potential to be especially harmful to the Republicans not only because of the spectre of inappropriate sexual behaviour with young people, but because it raises significant questions about the failure of the party's leadership in the House to address the issue.

Republican House of Representatives Speaker Dennis Hastert and his aides have been criticized for failing to act promptly after receiving warnings about Foley's questionable electronic communications with pages.

Several recent polls have shown declining approval ratings for Republicans in the last week amid an onslaught of questions about how the party's congressional leaders handled the Foley issue.

The USA Today poll found two-thirds of respondents were following the Foley scandal very or somewhat closely.

More than half, 54 per cent, believed Republican leaders who knew about Foley's behaviour did not act against him earlier "for political reasons."

The CNN poll found 52 per cent believed Hastert should resign, while the CBS poll found 46 per cent wanted his resignation.

The CBS poll found two-thirds of voters said the Foley scandal would make little difference in how they cast their ballots but 21 per cent said it would make them more likely to vote for the Democrats.

The ABC poll found that the Foley scandal was less of a concern than Iraq for voters, who doubted whether Democrats would have been better able to handle the scandal.

The poll also found that 63 per cent of respondents said the Iraq war was not worth fighting, which represented a new high for that poll.

A record for the poll was 53 per cent of respondents who disapproved of Bush's handling of the U.S. campaign against terrorism.

The CBS poll found the number of Americans who approve of Bush's handling for the campaign on terror dropped 8 percentage points over the past two weeks to 46 per cent.

The poll also showed that Americans are now evenly split over which party they think can better handle terrorism, marking the first time that Democrats have matched Republicans on national security.

The USA Today poll showed Bush's public approval rating at 37 per cent, down from 44 per cent in mid-September.

The approval rating for Congress was 24 percent, down 5 percentage points from last month.

The ABC News poll reported that Bush's approval rating registered at 39 per cent, down from 42 per cent early last month, which could pose a problem for the Republicans as they send him out on the road to rally support.

The CBS poll said Bush's job approval had slipped to 34 per cent, one of the lowest levels of his presidential tenure.

The poll found that 83 per cent of respondents thought the U.S. president was either hiding something or mostly lying when he discussed how the war in Iraq was going.

Of the respondents, 57 per cent said Bush was personally aware of pre-Sept. 11 intelligence reports that warned of possible domestic terror attacks using airplanes.

It marked an increase from May 2002, when 41 per cent said they thought Bush knew of the reports.

Government corruption, Iraq and terrorism were the three most important issues listed in the USA Today poll, with respondents saying Democrats would do a superior job on all points.

Democrats had a 21-point edge on dealing with corruption and a 17-point lead on Iraq.

The traditional Republican advantage on handling terrorism disappeared, USA Today said, with Democrats holding a 5-point edge.

When asked which party's candidate they would support if the election were held today, the USA Today poll found Democrats were favoured by 23 percentage points among all voters questioned, including likely voters, registered voters and adults.

The CNN poll found 58 per cent of likely voters say they plan to vote for Democrats in November while 37 per cent said they will vote for Republicans. The 21-percentage point edge is 5 points higher that it was in a CNN poll last week.

Americans vote for Congressional representatives on a fixed date every two years.

This year, 33 of 100 Senate seats are at stake.