Midnight train to Pennsylvania

"In television commercials and in appearances before crowded rallies, Mr. Obama, of Illinois, cast his opponent in one of the most negative lights of the entire 16-month campaign, calling her a compromised Washington insider," the New York Times reported.

Clinton responded "by suggesting that Mr. Obama's message of hope had given way to old-style politics and asked Democrats to take a harder look at him," the Times reported.

"The volleying in the final hours reflected the high stakes in Tuesday's contest," the Washington Post reported. "Clinton is favored to win, but the senator from New York may still face renewed pressure to end her candidacy unless she rolls up a sizable margin in the popular vote and significant gains in the overall delegate count," the paper reported.

Obama accused Clinton of using a "kitchen-sink" approach to attack him. "You learned the wrong lessons from those Republicans who were going after you in same way using the same tactics all those years. I don't want us to become like them. I want us to change the country," Obama said.

But Clinton accused Obama of being "negative" and using GOP tactics to distort her health care proposal. "He has sent out mailers, he has run ads, misrepresenting what I have proposed," she said. She told a crowd in Pennslyvania that "the last thing we need is to have somebody spending as much money as he has downgrading universal health care."

Voters in Pennsylvania go to the polls on Tuesday, the first Democratic primary contest in six weeks. Every recent poll shows Clinton leading in the state, with a margin ranging from 3 to 10 points.