Washington - No matter who the next resident of the White House is, his ability to institute his agenda will depend largely on what happens in hundreds of congressional races across the United States.

Democrats hope that strong interest in presidential candidate Barack Obama, 47, and dissatisfaction with President George W Bush will help them to widen their current 236-seat majority in the lower House of Representatives and their razor thin edge in the upper Senate.

Republicans on the other hand have focused largely on stopping the bleeding of a party flayed by Bush's unpopularity and a floundering economy.

Although incumbents generally have major advantages in retaining their positions in Congress, Republicans face a greater challenge than usual from the outset because of a large number of representatives retiring from public life or seeking other office - 29 Republicans to just six Democrats in the House.

All 435 seats in the House of Representatives are up for grabs as they are every two years, while just a third of the 100-member Senate needs to be filled.

Democrats have enjoyed advantages in fundraising, with 466 million dollars for House races to the Republican's 385 million dollars. In the Senate, Democrats have the advantage of 226 million dollars versus 157 million dollars for Republicans, according to the Federal Election Commission.

But even though Republicans have been battered in the public opinion, Democrats in control of Congress are not receiving any love either. They gained power just two years ago on a wave of anti-war, anti-Bush sentiment. But in the face of an opposition president and without the necessary votes to override his veto, they have since done little to change the status quo, earning them the moniker "do- nothing Congress."

A summary of opinion surveys by realclearpolitics.com finds 75 per cent of people disapprove of the job the legislature is doing, worse than Bush's 67-per-cent disapproval rate.

Even so, Republicans look set to be the big losers on November 4. A calculation by Congressional Quarterly magazine says 23 races in the House and four in the Senate are basically too close to call. Internal party documents cited by the Politico newspaper show Republicans believe 58 House seats are at risk, including 11 that have already been written off as lost and 34 more that are in serious jeopardy.

Among the races to watch:

- Minnesota Senate - Republican Senator Norm Coleman faces off against outspoken political comedian Al Franken on the Democratic side. Coleman has criticized Franken for his lack of experience and crude jokes, while Franken has painted the moderate Coleman as a rubber stamp for Bush. Dean Barkley, a third party candidate from the Independence Party of former professional wrestler and governor Jesse Ventura, could sway the race.

- North Carolina Senate - Senator Elizabeth Dole should be safe in the conservative southern state, but the experienced politician and former Red Cross head who is also the wife of former senator and presidential candidate Bob Dole, is facing a tough challenge from Kay Hagan, a senator in the state legislature.

- Kentucky Senate - In a sign of Democratic confidence, Bruce Lunsford is going after powerful Senate Minority Leader Mitch McConnell in traditionally Republican Kentucky. Though polls show McConnell, who has served in the Senate since 1984, is ahead, Republicans are fighting hard to hang on to the seat with a cross- state bus tour and a rash of ads.

- Alaska Senate and House - Just a week before the election, long- time Alaska Senator Ted Stevens was convicted on corruption-related charges for allegedly concealling improper gifts, leaving an opening for Democrat Mark Begich. Representative Don Young has also been caught up in an influence- peddling investigation involving an oil company and much of the state's Republican Party. He faces Democratic challenger Ethan Berkowitz.

- Minnesota House - Republican Representative Michelle Bachman, a frequent conservative voice on the television talk show circuit, faces a battle after incendiary remarks calling Obama and Democratic members of Congress "anti-American." The resulting controversy drew in a flood of Democratic campaign donations to opponent Elwyn Tinklenberg and could cost Bachman the election she once looked certain to win. The national Republican Party even yanked financing of ads in the race.

- California House - Though the economy has trumped the war in Iraq as a national issue, in a California House race outside San Diego - home to a large naval base - it could play a larger role. The contest pits two veterans of Iraq and Afghanistan: Republican Duncan Hunter, a retired Marine who is also the son of the area's current retiring congressman, and Democrat Mike Lumpkin, a retired Navy Seal with 21 years of military service.

- Florida House - Republicans' only sure chance of taking back a seat from the Democrats involves scandal-plagued Representative Tim Mahoney, who is battling a series of adultery allegations that include paying off a former employee to keep quiet about the affair. His opponent Tom Rooney looks set to cruise to a landslide victory.