Pennsylvania, it’s sometimes said, can best be understood as Philadelphia and Pittsburgh separated by Alabama. Geographically speaking it’s a big state in the heart of the liberal Northeast, home to great universities, Ben Franklin and the Liberty Bell, anchored by a great Eastern metropolis at one end and a once-booming Midwestern steel town at the other. Everything in between, though, is rural, gun-totin’, Bible-thumpin’ country.

It’s no surprise, then, that every peculiarity of America’s perpetual religious quarreling seems to collide in Pennsylvania. It was founded as a haven for religious dissenters by Quaker leader William Penn, who envisioned Philadelphia as a city of brotherly love. It is the cradle of American tolerance, where Thomas Jefferson wrote the Declaration of Independence, where the Constitution and Bill of Rights were signed. More recently, it was the scene of a celebrated court battle over a local school board’s effort to make biology students learn divine creationism — they called it Intelligent Design — in a town called Dover, just above the Mason-Dixon Line.

And it is the home state of Rick Santorum, the scrappy ex-senator who has made his distinctive religious views the centerpiece of his underdog Republican presidential campaign.

If he succeeds, it will mark a notable advance for minority religious believers in this country. He will be only the second Catholic ever to reach the White House, following in the path cleared for him by another senator from the Northeast, John F. Kennedy.

You’ve probably heard by now about Santorum’s homage to the martyred president who made his candidacy possible. Kennedy famously flew to Houston on September 12, 1960, to reassure a gathering of mostly-Southern Baptist ministers that he would not threaten the separation of church and state (yes, Southern Baptists used to worry about such things) by taking orders from priests. The first time Santorum read that speech, he told a Catholic college last October, he “almost threw up.”

As the cradle of American political-religious mudslinging, Pennsylvania has naturally been ground zero in the contest for the Jewish vote. Indeed, it was the site of America’s very first public effort to woo Jews away from the party of Thomas Jefferson and Franklin Roosevelt. The candidate in question was Jefferson. It was 1800, the first presidential election featuring political parties. Jefferson headed the newly formed Democratic-Republican Party, today’s Democrats. That fall a Federalist newspaper in Philadelphia, the Gazette, published an article by one Moses S. Solomons warning his fellow Jews that Jefferson, the nation’s leading advocate of church-state separation, was an enemy of “all religion.”

The Federalist ploy fizzled when the city’s lone synagogue, whose president was a fiery Jeffersonian named Benjamin Nones, announced that “[n]o such man as Moses S. Solomons” had “ever been” (their emphasis) a member of the Jewish community. It couldn’t have helped the Federalists’ cause that the Gazette had attacked Nones that summer as part of “the filth of society,” being “a Jew, a [Democratic-] Republican, and poor.” This prompted Nones’ famous reply: “How then can a Jew but be a Republican?” (meaning, confusingly, a Democrat).

Politicians have been trying to loosen that bond ever since, usually without success. Abraham Lincoln tried in 1860, asking Chicago lawyer Abe Jonas to spearhead an effort. It failed. Ulysses S. Grant tried recruiting banker Joseph Seligman as his secretary of Treasury, but was turned down. With rare exceptions, the combination of Jefferson’s secularism, Andrew Jackson’s economic populism and Woodrow Wilson’s internationalism have kept Jews’ loyalty firm.

GOP hopes have risen in recent decades, spurred by rising Jewish affluence and self-assurance. Dwight Eisenhower drew 40% of Jewish voters in 1956; Ronald Reagan won nearly that in 1980. Since then, though, Republicans have been trending relentlessly downward.

The current slide may have begun on September 12, 1991. That day, then-president George H.W. Bush unwittingly marked the 31st anniversary of Kennedy’s historic speech by publicly attacking a gathering of Jewish citizen-lobbyists as “some powerful political forces.” The slur outraged Jews nationwide, unleashing a flood of donations that helped defeat the Republican candidate in a special senatorial election nine weeks later in — where else? — Pennsylvania. The Republican, embarrassingly, was Bush’s own attorney general, popular ex-governor Dick Thornburgh. The winner was Harris Wofford. He was defeated three years later by Rick Santorum.

Obama’s troubles have lately reignited GOP hopes. In February, the Pew Forum on Religion and Public Life published a survey showing that Jewish identification with Republicans had risen from 20% in 2008 to 29% now. But the survey included a mere 334 Jewish respondents, giving it a high margin of error. Moreover, it was conducted last fall, before Santorum’s surge. Even if he ends up losing, he’s probably ruined the Republican brand among Jews for another generation.

Will it ever change? If it does, it will start in Pennsylvania, still ground zero for Jewish partisan fighting. Consider the Bush debacle of 1992, for example. That was the beginning of a Jew-vs.-Jew seesaw battle, then a rarity, in the heavily Jewish 13th congressional district outside Philadelphia, where Democrat Marjorie Margolies-Mezvinsky narrowly defeated Republican Jon Fox, then promptly lost to him in 1994. Jew-vs.-Jew seesaws are more common now, but none tops the Minnesota senatorial seat held successively since 1978 by Republican Rudy Boschwitz, Democrat Paul Wellstone, Republican Norm Coleman and now Democrat Al Franken, with nary a gentile in the mix.

In the end, of course, the struggle for the Jewish vote is really a battle for the Jewish soul. To understand it, look no further than the long-running Pennsylvania seesaw between onetime Democratic Philadelphia district attorney Arlen Specter, long-serving Republican senator Arlen Specter and now-defeated Democratic senator Arlen Specter. His path recalls nothing so much as Yogi Berra’s comment upon learning in 1956 that a Jew, the great Bobby Briscoe, had been elected Lord Mayor of Dublin: “Only in America.”