Voters go to the polls in Pennsylvania in a make-or-break Democratic primary today. Wait — where have I heard this before? Oh, yes, in March with Texas and Ohio. Hillary Clinton hopes to win big enough in Pennsylvania after six weeks of simultaneous brawling and whining with Barack Obama to justify another few weeks of the same :

The six-week Pennsylvania primary drew to a contentious finish Monday as Senator Hillary Rodham Clinton invoked images of Pearl Harbor and Osama bin Laden in a television advertisement that questioned Senator Barack Obama’s ability to lead in a crisis.

As she sought to spark a comeback in the Democratic nominating contest, Mrs. Clinton warned voters not to “take a leap of faith or have any guesswork” when they cast ballots Tuesday.

The Obama campaign accused her of employing “the politics of fear.” …

Pennsylvania has become a major battleground in the fight for the Democratic presidential nomination, with the future of Mrs. Clinton’s campaign most likely resting on the outcome. Even a wide victory by her would not overcome her deficit in pledged delegates or in the popular vote of states that have held nominating contests, but it would ensure that the race moved on to contests in Indiana and North Carolina in two weeks, on May 6.

Obama’s complaint about the “politics of fear” certainly proved valid with Obama himself. He abruptly canceled the final scheduled debate in North Carolina, publicly citing scheduling difficulties. On background, his aides spun it as an aggressive attempt to force Hillary out of the race, but everyone else understands that Obama wants to avoid another prime-time beating in front of the nation. It’s hardly complimentary to his sense of courage that Obama wants to start ducking confrontations at this point of the campaign, especially in friendly territory like North Carolina.

Analysts will watch the results closely to determine if Hillary performs well enough to survive. She certainly has to win here in order to keep the party elders from making the long walk and demand her withdrawal. How much of a win does she need to remain credible? Having led in this state by as much as 16 at one point but falling behind in more recent polling, will a thin victory show resilience or weakness?

My prediction: Hillary wins Pennsylvania by eight. I suspect that Obama’s support in Philadelphia will keep him competitive, but the twin blows of Crackerquiddick and his awful debate performance will have convinced Pennsylvanians that Obama needs more experience — a lot more experience. An eight-point victory will legitimately keep Hillary in the race, and allow her to coast past North Carolina and look to Indiana for the next make-or-break. Anything larger will call into question whether Obama might need to start looking at make-or-breaks, too.

We’ll be covering tonight’s primaries in a live blog. Stay tuned!