With Democratic majorities in the House and Senate in increasing jeopardy, President Barack Obama rallied thousands of supporters in Philadelphia this morning, the first of three scheduled campaign stops on the final Saturday before voters head to the polls.

Addressing an audience of thousands at Temple University, the president warned that Republican gains on Tuesday could reverse recent progress in the nation’s health care system and the economy.

“You cannot stop now, because the fact of the matter is we are in a difficult election. It’s difficult here in Pennsylvania. It is difficult all across the country,” Obama said shortly before noon, sharing a stage with Democratic Senate nominee, Rep. Joe Sestak and gubernatorial hopeful Don Onorato.

“And unless each and every one of you turn out, and get your friends to turn out, and get your families to turn out, then we could fall short, and all the progress that we’ve made over the last couple of years can be rolled back.”

It’s no accident that the president began his day in Pennsylvania, an always-battleground presidential state that this year features at least 10 competitive House races, in addition to closely fought contests for governor and Senate.

The president also will hold rallies in Connecticut and then in Illinois, states with competitive Senate races and a growing field of contested House seats. Top hip-hop stars will join him on each stage as Democrats attempt to engage young voters who helped elect him in 2008.

After speaking to the Philadelphia crowd of roughly 1,600 inside a Temple University gymnasium for less than 10 minutes, Obama made an unscheduled stop at the Famous 4th Street Delicatessen in Philadelphia’s Queen Village neighborhood.

The lunch stop surprised patrons, who mingled with the president, posed for cell phone pictures and shook his hand, before Obama ate a corned beef sandwich with potato pancakes, according to a pool report.

The president was set to address another rally in Bridgeport, Conn., this afternoon. A similar Chicago rally was scheduled to begin at 6:45 p.m.

The White House carefully crafted the travel schedule for the president, whose party is bracing for massive losses in the House and a potential loss of the majority in the Senate, as new polls in Colorado and Washington suggest a worsening outlook for Democrats.

The president will continue campaigning Sunday, when he will make an early afternoon stop in Cleveland alongside Vice President Joseph Biden. Democrats have all but conceded the Senate contest in the Buckeye State, but the gubernatorial race and a host of House contests still hang in the balance.

And while Obama’s schedule is still evolving as Tuesday’s election looms, he’s added a telephone town hall event to help benefit New Hampshire Democratic Senate candidate Rep. Paul Hodes, who’s trailing his Republican opponent, former state Attorney General Kelly Ayotte.

The Hodes campaign confirmed today that the president will host a “telephone town hall” with supporters at 7:50 p.m.

Meanwhile, back in Philadelphia, Obama reminded supporters of what’s at stake this Tuesday.

“It is absolutely critical that you go out there and you describe your hopes for the future, especially the young people here, because this election is not just going to set the stage for the next two years,” said. “It’s going to set the stage for the next 10, for the next 20.”