NBC NEWS- Voters in Pennsylvania go to the polls Tuesday and decide where the democratic nominating process goes from here.

Barack Obama’s campaign has all but conceded that Hillary Clinton will come out ahead.

What he wants to do is deprive her of a big win that could help her claim to be more electable in November.

Fighting for the last word before Tuesday’s vote, Hillary Clinton rallied students in Philadelphia late Monday night.

Clinton said, "Not enough to say 'yes we can' but 'how we will'."

Barack Obama, challenging Clinton was back in McKeesport Monday night.

"Senator Clinton does not recognize the need to fundamentally change how Washington works," Obama said.

Both candidates defend the campaign's increasingly tart tone with days of not-so-veiled barbs on the stump and on TV.

Both candidates were interviewed by NBC’s Ann Curry.

On Tuesday portions of those taped interviews were played on NBC’s Today Show.

Curry asked Clinton, "People think you've gone too negative."

Clinton responded, "I just don't buy that. I think people in Pennsylvania want a vigorous campaign where the contrasts are clear."

Curry asked Obama, "How are these comments not the same old style politics you accuse her of?"

Obama responded, "Somebody attacks you and attacks you and attacks you and when you finally call them on it, suddenly you're engaging in the same tactics."

In the six week-lead up the Democrats have crisscrossed the state, debated and made controversial gaffes, Clinton on sniper-fire in Bosnia, Obama calling some voters bitter.

The candidates with humor also made their pitch to wrestling fans of the WWE with a taped message played at Monday night’s Smackdown event.

In the spot Clinton said, "This election is starting to feel a lot like king of the ring. The only difference is, the last man standing may just be a woman."

Obama said, "I’ve got one question: do you smell what Barack is cooking?"