HARRISBURG - On the airport tarmac a little after 6 p.m. Sunday, Sen. Hillary Rodham Clinton was sleeping in the front row of her campaign's chartered Boeing 717, her feet propped up on the bulkhead, two bags stuffed with briefing binders on the seat next to her.

It was a rare moment of peace for a woman fighting to keep alive her presidential candidacy in Tuesday's Democratic Pennsylvania primary. On the trail, Clinton has adopted the determined persona of Rosie the Riveter, the iconic World War II defense-factory worker whose motto was "We Can Do It!"

She pushes on in the face of a deficit in the delegate count that seems impossible to overcome, as pundits and some Democratic leaders fret that she can only postpone Sen. Barack Obama's inevitable victory and weaken the party.

At recent campaign appearances from Aliquippa to Scranton to Philadelphia, Clinton talks about "fighting" for working people, jabs her opponent, and describes herself as somebody who can take a punch.

"I know what it's like to stumble. I know what it means to get knocked down," Clinton said at a Beaver County Democratic Party dinner at the Fez, a catering hall in Hopewell. "But I will never stay down," she continued, as the audience's cheers reached a crescendo. "I never will, and neither will America. . . . Strength matters in a president."

While some see a risk of seeming too combative, Clinton seems comfortable in the scrappy role. Strategists believe that voters relate better to the woman trying so visibly to win their support than they did to the prohibitive front-runner earlier in the campaign.

Staffers three decades her junior say the 60-year-old senator exhausts them during 16-hour campaign days. People who know her say she sometimes voices frustration, but does not wallow in it.

Showing her fighting side has paid off for Clinton before.

In New Hampshire's January primary, she came from behind to win after she grew emotional at an event and declared that "politics is not a game" to her. Obama racked up 11 straight victories in primaries and caucuses in February, and Clinton came back to win Ohio by wooing working-class voters. "Shame on you, Barack Obama," she said after his campaign attacked her on trade issues. "Meet me in Ohio!"

A Quinnipiac University poll of Pennsylvania voters released yesterday showed Clinton leading Obama 50 percent to 44 percent - unchanged from the week before, which was good news after several weeks that saw her lead in the state shrink.

Late Friday, Clinton received a gift: remarks Obama made at a San Francisco fund-raiser in which he said small-town Pennsylvanians "cling to" religion, guns and xenophobia to ease their frustrations over job loss. She and her campaign seized on the remarks to paint Obama as an elitist who cannot win swing states in the fall.

"We can't afford for people to believe that the Democratic Party is out of touch," Clinton said Sunday morning in Scranton. "Honestly, how do we expect people to listen to us if we don't hear them and we don't respect their values and their way of life?"

The Clinton team's last best hope is to build the case to superdelegates that Obama is unelectable, and his appearing to disrespect swing voters presented a powerful argument for that. Still, pollsters said it was too early to assess whether the controversy has damaged Obama in Pennsylvania; Gallup's daily tracking polls indicate it has not halted his momentum nationally.

And there is a risk for Clinton, analysts say: that her attacks on Obama remind voters of what they did not like about the Clinton White House years - the constant spin, the win-at-all-costs mentality of the "war room."

A Gallup poll last month showed just 44 percent of Americans believed Clinton to be "honest and trustworthy," compared with 63 percent who described Obama as such, and 67 percent who called presumed GOP nominee John McCain honest. A recent Pew Research Center survey showed that 44 percent of voters had a somewhat or very negative view of Clinton.

"People like a fighter, but they don't like someone who is caustic," said Chris Borick, a pollster at Muhlenberg College in Allentown. "She has to run the risk, because she is running out of time and running out of options to change the dynamic of the race."

Lucy Mathlage, a supporter at the Beaver County dinner, said she still thought Clinton could win and hoped she would continue fighting.

"She's been there and done that, and understands the crises we're in here," said Mathlage, 70, a social worker.

The New York senator also got encouragement as she campaigned among the rowhouses late Sunday afternoon along Francis Street in Drexel Hill, Delaware County. She signed autographs, posed for pictures, heard people tell her to keep fighting.

"She has middle-class values," said Jill Rementer, 48, a nurse educator. "She understands us."

Marie Hoban, 67, praised Clinton's "experience and compassion." She gave the candidate a tight hug.

"I told her, 'You have to win - we need you, don't give up,' " Hoban said afterward.

Contact staff writer Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews.com.