Democratic challenger Tom Wolf leads Gov. Tom Corbett (R) by 17 percentage points among likely voters in Pennsylvania – 55 percent to 38 percent – as the campaign enters its final month, according to a Quinnipiac University Poll released Tuesday.

The survey shows a slight improvement for Corbett compared to the last Quinnipiac Poll of the race Sept. 11, when Wolf led 59 percent to 35 percent among likely voters.

"With a slight shift in the numbers as a handful of Republicans come back, there is a pinprick of light at the end of the long, dark reelection tunnel, but time is not on Pennsylvania Gov. Tom Corbett's side," said Tim Malloy, assistant director of the poll. "It's a matter of simple math."

Republicans back Corbett 75 to 22 percent, one of the lowest rates of same-party support for an incumbent governor in any of the nine states surveyed by Quinnipiac University.  That's an improvement over last month, when Corbett led 66 to 28 percent among GOP voters.

The survey is based on live interviews with 907 likely voters, with a margin of error of plus or minus 3.3 percentage points. Voters with both landlines and cell phones were contacted.