Hillary Clinton and Barack Obama will be fighting each other for the Keystone State's 158 delegates. But they'll also be fighting a common foe: A growing belief that neither can win the general election in November.
It's a problem Clinton has had all along, and Obama, despite being the front-runner, is now proving he belongs in the same soup.
Clinton started with half of America's voters saying they would never support her for President, and the number hasn't budged. Against Republican John McCain, she would have to win virtually every voter who hasn't already decided against her.
Obama is closing in on her dubious distinction. His slam against small-town Americans, saying they "cling to guns and religion" out of bitterness over the economy, is certain to cost him in Pennsylvania among the white working-class voters he had trouble attracting in other states.
Already facing a racial barrier made worse by the incendiary comments of his pastor, the Rev. Jeremiah Wright, the notion that Obama is also a liberal elitist could prove fatal in swing states. Clinton was quick to make that point in blasting his "cling to guns and religion" remarks.
"We had two very good men, and men of faith, run for President in 2000 and 2004," she said, referring to Al Gore and John Kerry. "But large segments of the electorate concluded that they did not really understand or relate to, or frankly respect, their ways of life."
Clinton knows she's right because she has similar problems. She and hubby raked in $110 million in the last seven years, a staggering amount of dough that a photo-op with a shot and a beer can't erase. She is far more liberal than these Reagan Democrats and, we shouldn't forget, she is a she.
The odd part is that the Democratic demolition derby leaves McCain as the one candidate widely considered electable. In a year where Dems supposedly were unstoppable, they could lose a sure thing.
The latest Rasmussen Reports daily tracking survey shows McCain narrowly beating both Obama and Clinton. More important, it finds that 53% voters view McCain favorably, while 45% view him unfavorably. Obama's ratings are 49% favorable and 49% unfavorable, while Clinton's are 43% favorable and 54% unfavorable.
A comforting notion for Dems, that the winner of the nomination will unite the party, might also be an illusion. One in four Clinton voters would go for McCain if Obama wins the nomination, while about one in five Obama voters would back McCain if she wins the nomination, according to one survey.
Even worse for Obama, if his small-town slam and his ties to Rev. Wright hurt him in the upcoming primaries of Indiana, Kentucky and West Virginia, it could mean he's doomed in the Electoral College.
As John Judis writes in the New Republic: "To win in November, a Democratic presidential candidate has to carry most of the industrial heartland states that stretch from Pennsylvania to Missouri. That becomes even more imperative if a Democrat can't carry Florida - and because of his relative weakness in South Florida, Obama is unlikely to do so against McCain."
Judis estimates Obama would have to win a minimum of 45% of white votes in the heartland states, and a majority in some to build an electoral majority.
But in Ohio, a battleground state that Clinton carried by 10 points, an exit poll shows Obama got only a third of white voters. A breakdown by author Jay Cost finds that Obama lost nearly all the Ohio districts to Clinton that determine who wins the state in the general election, some by as many as 25 points.
Of course, the past doesn't guarantee the future. That's what campaigns are about. But they do show that the soaring Obama candidacy is coming back to Earth and landing in an all-too familiar spot for Democrats.