After having lagged by as much as twenty-three percentage points this election season, Republican Senator Rick Santorum now trails Democrat Bob Casey, Jr. by only eight, 40% to 48% (see crosstabs).

Until now the incumbent has failed to pull within single digits of his opponent. Last month, Santorum suffered an eleven-point deficit in our poll, which he'd shaved from fifteen points in June. But Santorum had also been eleven points behind in March...a gap that in May more than doubled.

This poll has shifted Pennsylvania from “Democrat” to “Leans Democrat” in our Balance of Power summary.

Senator Santorum is still a point behind his best support level of the year. It's a slight dip in Casey's support that has allowed Santorum to draw as close as he is now. That dip might have something to do with recent ads attacking Casey's record as State Treasurer.

A third-party candidacy may also affect the outcome, with 5% of likely voters now supporting Green Party candidate Carl Romanelli. However, it’s worth noting that “some other candidate” attracted 5% of the vote in our previous Pennsylvania poll. Overall, it appears that the shift in the race results from declining enthusiasm for Casey more than any other cause.

If Romanelli’s support grows, it is likely to draw votes from Casey. To the annoyance of Democrats, Romanelli’s petition drive has been helped by money and manpower from the Santorum campaign. Democrats have been urging Romanelli to drop out.

Casey may be more vulnerable to a third party candidate than other Democrats because of his pro-life position on the issue of abortion.

With a favorable rating of only 45%, unfavorable of 48% (29% "very" unfavorable), Senator Santorum is still very vulnerable. But like Republicans generally (see the analysis of the Generic Ballot at Scott's Page), he doesn't look quite as weak as he did just a couple months ago. And the Senator is definitely a scrapper.

Casey is now viewed favorably by 58% (most of that support still in the "somewhat" favorable category), a decline from 66% in July.

Senator Santorum is viewed as conservative by 60% of all voters, Casey as liberal by just 29%. Forty-five percent (45%) say Casey is moderate.

Forty-five percent (45%) of the state's likely voters say the U.S. and its allies are winning the war on terror. Thirty percent (30%) say the terrorists are.

Crosstabs are available to Premium Members.