Former congressman Mike Fitzpatrick leads Rep. Patrick Murphy, 49 percent to 35 percent, in one survey in suburban Philadelphia's 8th District race, the seat Fitzpatrick held until Murphy beat him by a thin margin in 2006.
Pollster G. Terry Madonna says that waning support for President Barack Obama has hurt Murphy. Obama carried the district in 2008.
Murphy's campaign questioned the reliability of the poll, citing a 2006 Franklin & Marshall survey that showed Fitzpatrick with a similar lead in the election he ultimately lost. Murphy campaign manager Tim Persico said other polling shows Murphy with a four-point lead in a race that was expected to be tight.
Fitzpatrick campaign spokesman Darren Smith said the poll backs up what its workers are hearing from voters.
"Voters are rejecting the failed policies of congressman Murphy and Nancy Pelosi and their inability to improve the economy or rein in the jobless rate," Smith said.
The 8th District poll of 379 likely voters had a margin of error of 5 percentage points.
The poll was conducted Sept. 14-19 by telephone.