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.