Bill Clinton, one of the biggest guns in his party's arsenal, swept through Pennsylvania Monday, rallying crowds for President Obama as Democrats tried to hold off Republican Mitt Romney's late bid to win the state.

Former New York City Mayor Rudy Giuliani toured the territory as well, urging Republicans in the Philadelphia suburbs to give Romney an upset here that could change Tuesday's electoral math.

Fresh from a huge Bucks County rally Sunday night, Romney added a stop in Pittsburgh on Election Day, signaling how hard he is pushing to win the state and perhaps carve a new path to victory. Former President Clinton's whirlwind visit in the final hours before polls open showed the urgency of the Democratic response.

"I want you to vote for hopes and not your fears. I want you to imagine what America can be like 10 years from now, and I want you to go out and make Barack Obama president for four more years," Clinton told a crowd of about 9,000 at the University of Pennsylvania's Palestra.

His voice hoarse but his hand gestures fully fit, the former president had supporters laughing and roaring. Using his raspy, folksy delivery as he spoke to a mostly young crowd, Clinton highlighted Obama's work to expand student loans, back women's rights, and overhaul health care.

"If, but only if, you reelect President Obama tomorrow, next year 30 million people, many with preexisting conditions, will be able to get insurance for the first time," said Clinton, wearing a dark suit and wine-red tie.

He accused Republicans of trying to bring back trickle-down economics. "They want to do it all over again," he said.

People were turned away at the door of the crowded arena, according to Penn's fire marshal. Romney, in a show of GOP enthusiasm, pulled an estimated 25,000 to Bucks County on Sunday.

Romney and Clinton's appearances came as Pennsylvania figured ever more in both sides' calculations. If Obama wins in Ohio, where he holds a razor-thin lead in polls, Romney would almost certainly need Pennsylvania's 20 electoral votes to win Tuesday.

Giuliani met with Conshohocken volunteers trying to flip the state to the Republican column in a presidential election for the first time since 1988. Entering a GOP campaign office to cheers, he said Obama's election had been a mistake, calling the president "an incompetent" and slamming his handling of Hurricane Sandy and the attacks on a U.S. diplomatic post in Libya.

"We're at a critical time for the country," Giuliani said. "Now there are no excuses - we can repair the damage that's been done to Pennsylvania."

Giuliani also made stops in Bethlehem, Scranton, and Wilkes-Barre. The actor Jon Voight joined him.

"We have a president who has failed us in many ways. The morale of this great country has never been at such a low level," Voight said in Conshohocken.

Matthew Stern, a Penn graduate student frustrated by high unemployment among young people, was energized by their visit.

"I'm really excited about the election. I took off work for two days," Stern said.

Meanwhile, Clinton went to the Democratic strongholds of Pittsburgh and Scranton as well as Philadelphia, and reached out to the suburbs at Montgomery County Community College in Blue Bell, where a line of supporters snaked across parking lots and tennis courts. Organizers scrambled to move the stage outside to accommodate the crowd.

At the Palestra hours later, with banners hanging from the rafters, Clinton's event took on the feel of a pep rally. Penn's pep band played as the crowd flowed in, snare drums and horns reverberating.

Clinton, on his third stop of the day, fought off coughs during his 31-minute speech, which mirrored the argument he made in September at the Democratic National Convention.

College tuition costs and social issues were the top priorities for many Obama supporters waiting to see Clinton at the Penn arena.

Ajon Brodie, a Drexel University student, said many friends had been forced to switch colleges because of rising costs, and he said he trusted Obama to make college more affordable. Brodie, 19, said he was drawn into politics by the election of the first African American president, and was eager to back Obama with his first-ever vote Tuesday.

"This is very exciting," he said.

Martin Harmer praised Obama's health care law. Without it, his 24-year-old stepson would be without health coverage, he said.

"I think it would be tragic if we lost that," said Harmer, 58, a Lehigh University engineering professor.

In Blue Bell, Valerie Tunstall Torrence, a home health care aide from Norristown, said of Clinton, "I came up and got better in my life when he was president. So if he's going along with Obama, I'm with Obama."