Donald Lambro

WASHINGTON -- Pennsylvania Sen. Rick Santorum has the dubious distinction of being the GOP's most vulnerable incumbent, but all that could change once Democratic voters know more about his pro-life opponent.

Virtually every poll shows Santorum running 10 to 15 points behind State Treasurer Robert Casey Jr., who is running a stealth, under-the-radar centrist campaign that is known more, in some circles, for his anti-abortion and gun-rights views than for anything else.

So far, Santorum has failed in his attempts to smoke Casey out on the issues, frustrating the two-term conservative senator, whose weak re-elect numbers have been frozen for months. Like Tom Dewey in the legendary 1948 presidential election, Casey is betting that the path to victory is to say as little as possible about what he thinks. In his case, though, it seems to be working for him.

But the big question is, how Casey's pro-life views, once fully known by the electorate, will play with the state's politically potent pro-choice voters, and whether an independent abortion-rights candidate can draw enough Democratic votes away from Casey to help Santorum eke out a victory in a divided three-way race.

Pro-choice leaders like former NARAL president Kate Michelman has whipped up opposition to Casey in her home state and for a while looked as if she would challenge him as an independent. She has indicated she will not run, but one of Casey's pro-choice opponents could.

"If there were a third-party candidate on the ballot who is pro-choice, that candidate could draw heavily from Casey backers among liberal Democrats, enough to make it a close race," said Clay Richards, assistant director of the Quinnipiac University Polling Institute, whose surveys show that Casey is very vulnerable on the issue among his party's base.

Although both Santorum and Casey are avowedly pro-life, the big difference is that the senator's position is strongly supported by the GOP's base, while Casey's party is overwhelmingly pro-choice in a state that has some of the most conservative abortion laws in the nation.

Strange as it may seem, most Democrats still don't know much about Casey's pro-life views -- including his opposition to federal funding of embryonic stem-cell research -- but when they do, his support drops. A Quinnipiac poll found that after voters were told he was pro-life, many Democrats reacted negatively to his candidacy, a fact that could spell trouble for him when the race heats up later this year.

Donald Lambro

Donald Lambro is chief political correspondent for The Washington Times.