"There's a big difference between talk and action . . . but if you are going to talk, you ought to mean what you say," Clinton told a cheering crowd of about 2,000 during a midday rally in Harrisburg.

Obama, who opened his Pennsylvania campaign in Bucks County, responded in an interview with The Inquirer, saying that on Iraq, Clinton was still "trying to finagle her way out of her misjudgments on the most important foreign-policy issue of our time."

He was back home in Chicago by the time he learned that he had won yesterday's Mississippi primary, the last event before Pennsylvania votes on April 22.

Clinton, on the second day of an in-state swing that concluded with a rally at Temple University, once again became the sharp-edged candidate who had attacked Obama's preparedness to be president before defeating him in Ohio and Texas last week.

In Harrisburg, she accused Obama of not being sincere about his pledge to withdraw troops from Iraq.

"My opponent said he'll have them all out in 16 months, and then one of his foreign-policy advisers says to the foreign press: 'Don't pay attention. That's just talk for the campaign,' " Clinton said.

It was a reference to a recent flap in which Samantha Power, an Obama adviser, told a newspaper in Scotland that candidates would not be bound by their campaign rhetoric in dealing with the Iraq war as president. She was forced to resign because she called Clinton a "monster" in the same interview.

Obama told The Inquirer that his commitment to a 16-month timetable was firm and unchanged.

"This notion that Sen. Clinton can twist the words of an adviser who's not even speaking in an official capacity on my behalf and try to tag them on me is the kind of politics that results in us not getting much stuff done," he said.

Clinton delivered a populist speech in Harrisburg, blasting oil companies, Wall Street hedge-fund managers, and health insurers, and vowing to make college more affordable. "We're going to have to fight to make the changes against the special interests that have dominated Washington," she said.

She drew cheer after cheer from the crowd, which included many state workers on lunch break wearing green AFSCME T-shirts. The public employees' union has endorsed Clinton.

She also criticized Obama for his visit to a Bucks County company that makes equipment that converts wind energy into electricity. She said it was hypocritical for him to talk about alternative energy after voting in 2005 for President Bush's energy bill, which gave tax breaks to oil companies.

"When he had a chance to say no to Dick Cheney and the oil companies, he voted yes," Clinton said. "I said no. He said yes."