Rep Tom Davis of Virginia, a former chairman of the House Republican campaign committee, said matters might get worse.

'The loss of three straight special elections, in once solidly Republican districts, cannot be explained simply by 'bad candidates' or by being out organized,' Mr Davis wrote in a private memo to House Republican leaders, a copy of which was obtained by Reuters.

'They (the losses) are canaries in the coal mine, warning of far greater losses in the fall, if steps are not taken to remedy the current climate,' Mr Davis said. 'The Republican brand is in the trash can.' With opinion polls showing voters favour Democrats on a host of issues, the party is expected to further swell its ranks in Congress in November, when Americans vote for a new president as well as all 435 House seats and a third of the 100-member Senate.

Republicans, who lost control of Congress to Democrats in 2006 elections, continue to be dogged by their unpopular leader, President George W. Bush, and his unpopular Iraq war.

They have also been hurt by Mr Bush's failed efforts to remedy the ailing economy and curb rising gas prices.

Republican presidential candidate John McCain, an Arizona senator, acknowledged the party's problems.

'We have to re-energise our base,' Mr McCain told reporters while campaigning in Ohio. 'We've got a lot of work to do. I have a lot of work to do.'

Democrats gained more political ground on Tuesday when they won a special election to fill a vacant seat in a conservative Mississippi district previously held by Republicans.

'It was another wake-up call,' House Republican leader John Boehner said. 'We have to show Americans that we can ... fix the problems that they deal with every day.'

Last week, in a special election to fill another vacant House seat, Democrats prevailed in a Louisiana district that Republicans had held for years.

In March, Democrats won a special election to fill the seat vacated by former House Speaker Dennis Hastert, an Illinois Republican who decided to retire early rather than serve out his two-year term in the new Democrat-controlled House.

Expanded democratic majority
House Republican leaders, shortly after receiving the Davis memo, gathered on the steps of the Capitol building for a scheduled event to try to rally their troops and US voters.

They showcased a package of largely old proposals to reach out to families, including measures to cut gas prices, make health care more affordable and crack down on street gangs.

'Our members are concerned but they are ready for the message we are rolling out this week,' said Mr Roy Blunt of Missouri, the Republican whip in the House.

Democrats mocked a new Republican slogan - 'Change you deserve' - by noting the phrase is used to market an antidepressant.

'Democrats, not drugs, is what the American people need,' said Mr Steny Hoyer of Maryland, the majority leader in the House.

With the election on Tuesday of Mr Travis Childers in Mississippi, Democrats will expand their House majority, controlling it 236 to 199.

Vice President Dick Cheney had campaigned against Mr Childers and Republican ads tried to link him to Democratic presidential front-runner Barack Obama, viewed by many Mississippians as too liberal.

'What happened in Mississippi yesterday was a day of reckoning for the failed policies of the Bush administration,' said the head of the Democratic congressional campaign committee, Rep. Chris Van Hollen of Maryland. -- REUTERS