President Obama, Gov. Christie Stump for Pennsylvania Gubernatorial Candidates

President Barack Obama tried Sunday adding a jolt of life into what has sometimes been a low-voltage Pennsylvania governor's race, telling supporters to vote for Democrat Tom Wolf and casting the election as a choice between trickle-down economics and policies that strengthen the middle class.

Obama's appearance, part of an eight-state campaign tour over the past couple weeks, comes two days before the election and was designed to stoke turnout in Pennsylvania's liberal bastion, Philadelphia. But Republicans seemed equally as pleased to see Obama, aggressively attacking him in a fresh campaign ad as Wolf's running mate.

Wolf, a first-time candidate who ran his family business for nearly three decades, is trying to knock off Republican Gov. Tom Corbett in Tuesday's election. Corbett, a conservative former state and federal prosecutor, is seeking a second term after stumbling through his first four years. In particular, Corbett has struggled to explain budget-balancing cuts in aid to public schools in 2011 at the same time he cut business taxes.

Philadelphia is a well-traveled city for Obama, and Corbett is particularly unpopular there. In a 20-minute speech, the president touted Wolf's experience as a businessman, and his support for raising the minimum wage, ensuring women get equal pay, expanding access to college and strengthening public education.

"The biggest corporations, they don't need another champion. The wealthiest Americans don't need another champion, they're doing just fine," Obama told a crowd of several thousand at Temple University's Liacouras Center. "But you know what's in need of a champion? Somebody who understands that opportunity for all is what America's all about, opportunity for all is what Pennsylvania's all about. And that's what Tom believes. But listen: Y'all have to vote. That's what this comes down to. You've got to vote!"

Without mentioning Corbett, Obama worked in digs at the governor. He touted the notion that Wolf will handle the economy better than Corbett — he brought up Pennsylvania's relatively slow rate of jobs creation, saying, "You don't want to be second to last!" And he cast Wolf as a practical businessman who sees education as the key to advancement.

"He knows for example that education is the key, not just to economic growth, but also to personal advancement in a modern economy," Obama said. "So he's not going to run on an agenda of slashing budgets for our schools or laying off thousands of teachers."

Wolf has led steadily in polls, although Corbett's campaign appears to be making up ground by warning voters that Wolf is secretly planning a massive middle-class tax increase. Wolf has said he intends no such thing and plans to restructure the state income tax rate to shift a bigger burden to higher earners.

Meanwhile, Corbett's campaign has added a second prong to its attack, attacking Obama in the days ahead of his visit in a TV ad in every market except Philadelphia that says "voting for Tom Wolf would be like voting to make Obama Pennsylvania's governor."

The ad tries to capitalize on Obama's sagging popularity — two recent independent polls show that just one in three voters surveyed say he's doing a good job.

Later, Corbett joined potential presidential candidate New Jersey Gov. Chris Christie at a campaign rally at Spring Mill Manor north of Philadelphia. Christie, who has made at least four campaign or fundraising visits to Pennsylvania for Corbett in recent months, told the crowd of several hundred that he sensed Democrats lack enthusiasm for Wolf.

Christie called Corbett "a tough competitor" and played up his credentials as a business-friendly candidate, saying he has lowered taxes, improved the business climate and attracted companies, including some from New Jersey.

Christie then mocked Obama's visit to Philadelphia, and made Obama an offer: He would send a plane to bring the president back to Pennsylvania to campaign because "one more half-baked rally with Barack Obama in Pennsylvania and Corbett will win in double digits."

To a large degree, the gubernatorial election will be won or lost in Philadelphia and its suburbs, home to one in three of Pennsylvania's nearly 8.3 million registered voters.

A high voter turnout in Philadelphia, the state's largest city, would favor Wolf, with Democrats making up almost 80 percent of the city's 1 million-plus registered voters. Also, the candidate who wins the four suburban counties is nearly assured of a victory.