The Democratic party faces another election test after the death yesterday of John Murtha, a congressman dubbed by his colleagues the "king of pork".
Murtha, aged 77, had been in the House of Representatives since being elected to his Pennsylvania district in 1974.
The fear in the party is that Republicans will notch up another victory when a special election is held, probably May.
The Democrats have been panicking since losing Ted Kennedy's Massachusetts Senate seat to the Republicans last month.
Murtha's nickname referred to so-called pork barrel politics – bringing government spending to bear in a representative's own district.
His death came on a day that saw Barack Obama's poll ratings fall further. A Marist poll found that only 44% of voters surveyed approved of his job performance, down 2% on December. More alarming for Democratic strategists, 57% of independents disapprove of his performance.
Murtha's death will have a negligible impact on the arithmetic of the House, where the Democrats have an overwhelming majority, unlike in the Senate. But another defeat in the spring would add to the sense of panic among Democrats in the run-up to the Congressional mid-term elections in November.
Murtha's office said he had died in hospital after complications following gallbladder surgery. He had been in hospital for several months.
His election in 1974 marked him out as the first of those to have served in Vietnam to make it into Congress.
He was popular on the left as one of the first senior Democrats in 2005 to turn against the Iraq war. But he was also one of the leading exponents of 'pork-barrel' politics, a practice that has long been reviled outside Washington and is one of the reasons for the present levels of disenchantment.
Murtha, as chairman of the House defence appropriations sub-committee, added 'earmarks', special spending projects to help his district, to defence bills, hence the King of Pork.
Scandal hovered over him throughout much of his career.
Murtha faced a tough race for re-election in 2008 after sabotaging his own campaign by referring to some of voters in Pennsylvania as "racist".
One of the reasons for the turnaround in Democratic fortunes is opposition to Barack Obama's health reform plan.
The president will make a fresh push this month to get his troubled health reform package through Congress by meeting both Democrats and Republicans, hoping to find common ground.
The half-day discussion at Blair House, opposite the White House, will be broadcast live on television to counter public criticism that too many deals in Washington are made behind closed doors.
Obama announced the meeting during a CBS television interview on Sunday evening. "I want to consult closely with our Republican colleagues … to ask them to put their ideas on the table. I want to come back and have a large meeting, Republicans and Democrats, to go through systematically all the best ideas that are out there and move it forward," he said.
The Republican leader in the House of Representatives, John Boehner, welcomed the move as "a real, bipartisan conversation", but added: "The problem with the Democrats' healthcare bills is not that the American people don't understand them; the American people do understand them and they don't like them."
The Republican leader in the Senate, Mitch McConnell, welcomed the meeting, but suggested he was unlikely to compromise, calling for the Democrats' bill to be shelved.
The move buys the Democrats a few more weeks while they debate among themselves whether to push forward with the bill or abandon it. The version of the bill passed by the Senate on Christmas Eve would extend health care to 30 million more Americans.