In some of the most pointed attacks of the campaign, the rivals unleashed TV ads accusing each other of being enthralled to the special interests they say they oppose.

At a rally in Johnstown, Clinton jumped on a comment that Obama made earlier in Reading that Republican nominee-in-waiting John McCain would be better than President Bush.

"We need a nominee that will take on John McCain, not cheer on John McCain," Clinton told a crowd of about 1,500 in the gym of Greater Johnstown Senior High School. She said McCain would continue Bush's "disastrous" fiscal and Iraq policies.

Though Obama did say McCain would be an improvement over the president, he also said that either Democrat would be better than McCain and predicted that Democrats would unite "because we cannot afford another George Bush, and that's what McCain offers."

He told a crowd of 2,600 at Reading High School that it faced a choice between the status quo and a new era of politics.

"What you have to ask yourself," he said, "is, who has the chance to actually, really change things in a fundamental way, so that 10 years from now, or 20 years from now, you can look back and say, 'Boy, we really moved in a new direction,' " Obama said.

Last night in Scranton, he said he "admires" Clinton but added: "Her basic message comes down to this: We can't really change our politics. . . . We might as well elect somebody who has been in politics a long time and knows how to play the Washington game."

Earlier, in Bethlehem, Clinton accused Obama of being "so negative" in his campaign tactics and of echoing Republicans in his televised take-down of her universal health-care proposal.

"He has sent out mailers, he has run ads, misrepresenting what I have proposed," Clinton said. "I really regret that because the last thing we need is to have somebody spending as much money as he has downgrading universal health care. We need to achieve universal health care - not create political opposition to universal health care. That's what the Republicans do."

In one of the rare policy differences between them, Clinton proposes that everyone be required to buy insurance coverage, while Obama would require it for only children. His ad says that Clinton would coerce people to buy something they cannot afford; she says that only universal coverage would spread enough risk around to lower costs.

On television screens across the state, viewers are witnessing dueling 30-second campaign commercials.

The Clinton camp released a spot accusing Obama of taking campaign cash from federal lobbyists for 10 years despite "boasts" that he does not, which has been one of his central campaign themes.

In a response ad, the Illinois senator shot back: "Barack Obama doesn't take money from special-interest PACs or Washington lobbyists. Not one dime. But federal records show Clinton's raised millions from PACs and lobbyists; more than any candidate, in either party." It called her spot an "eleventh-hour smear" funded by lobbyists.

Obama will have spent more than $9 million on television before the polls open tomorrow, to Clinton's $3 million. The intensifying bickering reflects the stakes of the primary. To many, Clinton needs an impressive victory to keep her campaign going in the face of the seeming impossibility of overcoming a delegate deficit.

Overall, Obama has 1,646 delegates to 1,508 for Clinton in the Associated Press count, with 2,025 needed to clinch the nomination.

An AP survey released yesterday found that 300 superdelegates had not declared a preference, and most said they would be guided by their judgment of which candidate would win in November, rather than primary votes.

After a whistle-stop trip aboard an Amtrak train on Saturday, Obama returned yesterday to a bus tour that began in Harrisburg, moved to Reading, and ended in Scranton.

Clinton used bus and plane to visit Abington, Bethlehem, Johnstown and State College yesterday.

The subtext of yesterday's flurry of charges and countercharges was last Wednesday's debate, in which Obama faced questions about his former pastor's inflammatory sermons, his friendship with a 1960s radical, the fact that he rarely wears a flag pin, and recent comments about small-town Pennsylvanians.

On the way from Harrisburg to Reading, Obama stopped at the Heidelberg Family Restaurant, where he fielded a question from Republican voter Margaret Miller, 66, of Newmanstown.

"May I ask you a question?" she said. "I'm going to ask you why you didn't salute the flag."

"That isn't true," he said, explaining that an "e-mail that's being sent around" featuring a photo from an event hosted by Sen. Tom Harkin (D., Iowa) last summer in Iowa is inaccurate when it claims he was disrespecting the Stars and Stripes.

"What happened was, we were singing 'The Star-Spangled Banner' and the flag wasn't in front of me, the flag was behind me," he said, adding that he was looking at the singer and that he always honors the flag.

"I had to ask," Miller said.

The Final Drive

Sen. Hillary Rodham Clinton and former President Bill Clinton are scheduled to appear at 10 p.m. today

at the Palestra at the University of Pennsylvania. Earlier in the day, she is

to be in Scranton, Pittsburgh and Harrisburg.

Sen. Barack Obama will make evening appearances in McKeesport and Pittsburgh.

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