In the latest Quinnipiac University poll, Rick Santorum still had a comfortable six-point lead over Mitt Romney in his home state of Pennsylvania. A new Public Policy Polling survey, though, shows Mitt Romney with a five-point lead over the former Pennsylvania senator.

Mitt Romney’s taken the lead in PPP’s newest poll of Rick Santorum’s home state of Pennsylvania. Romney has 42% to 37% for Santorum with Ron Paul at 9% and Newt Gingrich at 6%. The numbers represent a dramatic turnaround from when PPP polled the state a month ago. Romney’s gained 17 points, going from 25% to 42%. Meanwhile Santorum’s dropped 6 points from 43% to 37%, for an overall swing of 23 points in the last four weeks.

Pennsylvania Republicans are expressing major doubts about Santorum’s viability both in the primary and the general election. Only 36% of GOP voters think Santorum has a realistic chance at the nomination to 54% who believe he does not. And when it comes to matching up against Barack Obama in the fall only 24% of Republicans think Santorum would provide their best chance for a victory while 49% think that designation belongs to Romney.

Santorum’s favorability numbers haven’t really changed from a month ago. He was at 64/30 and now he’s at 62/31. But Romney’s seen quite a bit of improvement in his image, perhaps reflecting growing acceptance that he will be the nominee. His favorability has improved a net 16 points from +6 (46/40) to +22 (57/35).

Romney retains comfortable leads among seniors, men, “somewhat conservative” voters, moderates and suburban voters — and he’s made huge dents in Santorum’s leads among evangelicals, Tea Party voters and “very conservative” voters. As the PPP poll summary states, the race is still a close one, so Santorum could yet win — but the momentum favors Mitt Romney.

The real question, though, is this: Will Santorum risk a loss? With that devastating 18-point loss in the 2006 Senate race already on his record, will he want even a narrow defeat in his home state to be the next addition to his Wikipedia page? His rhetoric in recent days — particularly his invocations of the fighting spirit of Ronald Reagan, who lost his first bid at the presidential nomination — suggest he’d consider another run at the presidency in 2016. If he ducks out before a loss in Pennsylvania, he’d be an immediate contender in 2016, remembered as the man who gave Mitt Romney a real race. If he loses Pennsylvania, he might not be a contender at all in 2016, remembered as the man who held on too long.

A friend of the Santorum family suggests Santorum does not want to be remembered as that guy:

But one of Santorum’s close friends told The Hill that while the former Pennsylvania senator remains confident about winning his home state and using that to build May momentum, if that confidence falters, he might exit the race. Pennsylvania state Sen. Jake Corman (R), a longtime friend of Santorum and his family, said if it appeared Santorum wasn’t going to win the state, the former senator could drop his campaign.

“He’s a realist; he doesn’t have his head in the clouds,” Corman told The Hill. “As long as he sees a pathway to the nomination he’s going to stay in it, but he won’t stay in it to prove a point. If he gets to the point where he doesn’t think he’ll be the nominee, he’ll get out.”

(Meanwhile, James Carville calls Rick Santorum a “headless chicken.”)

The Santorum campaign’s own internal polling might show a different race in Pennsylvania, such that the candidate will compete regardless of what polls like this one suggest. If this is an accurate reflection of the state of the race in the Keystone State, though, I’d be surprised if Santorum hasn’t at least considered rethinking his “stay in until May at all costs” strategy.