In a poll this month by the Pew Research Center, 46 percent of seniors reported that they would be voting for the Republican on their congressional ballot this fall, compared with 43 percent for the Democrat. The most recent Gallup data showed an even starker difference: Fifty-three percent of seniors said they would vote for a Republican House candidate and 38 percent said they would opt for the Democrat.

“They are the voting group we are doing the worst with,” said Celinda Lake, a Democratic pollster. “They are also the voting group with the highest turnout in an off-year election. So it is going to be up to the individual members of Congress to go out there and make their case personally to seniors in their districts.”

The financial meltdown two years ago hit those of retirement age the hardest, and seniors remain slightly more negative about the Democratic-backed health-care overhaul than the general public, according to polls. A striking number of seniors, about 36 percent, believed the misconception that the law “allowed a government panel to make decisions about end of life care for people on Medicare,” according to a July poll by the Kaiser Family Foundation.