Former President Bill Clinton (search) took the stage to thunderous applause in Philadelphia Monday as he stumped for John Kerry's White House bid.

"If this isn't good for my heart, I don't know what is, thank you," said Clinton, who is recovering from quadruple-bypass surgery.

"You know, I'm very grateful to be here today and I thank all the people of Philadelphia and throughout the country for their e-mails and letters and prayers and support," Clinton said. "From time to time, I have been called the 'Comeback Kid' — in eight days, John Kerry's gonna make America the comeback country."

Clinton joined Kerry on the campaign trail in the City of Brotherly Love as former Vice President Al Gore (search) campaigned for Kerry in Florida.

"I know well that no one's presence can change a single vote, but I hope my reasons can affect a few votes," Clinton told the crowd in Philadelphia. "You've got a clear choice between two strong men with great convictions and different philosophies, different policies — with very different consequences for this city, this state, our nation and the world."

Pennsylvania has lost 70,000 jobs under Bush's watch, Clinton said, compared to the 219,000 gained "this time when that last fellow was president — me," he added.

The 249,000 people added to the poverty rolls since Bush took office, Clinton pointed out, contrast badly to the 395,000 who moved from poverty into the middle class the last time the country had a Democratic administration.

He added that the Bush administration's plan for the next four years was "more of the same."

Earlier, Clinton dismissed concerns that his decision to campaign for Kerry seven weeks after undergoing heart surgery was risky.

"I think you know there's only so much anyone else can do in a campaign that he or she is not the candidate in," Clinton said in an interview Sunday with ABC News. "But I want to do this. Senator Kerry asked me to do it. And I want to do it."

Clinton said he talked to his doctors about it and "they made some very helpful suggestions."

"They said, you know, I should get wherever I'm going early in case I'm tired, so I can kind of regenerate," he added.

He said his wife, Sen. Hillary Rodham Clinton (search), D-N.Y., was not worried that it would be too soon for him to campaign but "didn't want me to do too much, and I don't either," according to a transcript of the interview, which aired Monday on "Good Morning America."

The Bush camp said Kerry bringing out the big guns was a sign the Democratic candidate's campaign was flailing.

"I'm not sure they march out President Clinton from a position of strength," Bush-Cheney campaign spokeswoman Nicole Devenish told FOX News. "I think they felt it was important to roll him into some of these states that Gore won last time to maybe counteract some of the slippage they've had in some of those states."

But the Kerry campaign said it was not unusual to bring out the heavy muscle this close to Election Day.

"This is the time — there's nine days to go here, so you bring out everybody you can to bring out the vote," said Kerry senior adviser Michael Meehan. But "at the end of the day, it's John Kerry and George Bush who are on the ballot."

Former Vice President Al Gore (search) was also stumping for Kerry in Florida, the epicenter of the 2000 recount battle that lost Gore the presidency. Gore was making a two-day swing through the Sunshine State, targeting minority voters and urging them not to allow a repeat of the 2000 deadlock.

At a stop in Riviera Beach on Monday, Gore urged Florida voters on Monday to transform any leftover anger from the recount debacle into efforts to get out the vote early.

"Where do I start? Four years seems like four hours," Gore said. "We are in the same struggle for our country's future."

"Never again," activists chanted at a rally Sunday in Tallahassee, as Democrats waved signs "2000 Recount We Will Not Forget."

Gore was mixing a good dose of humor with his message.

"I flew on Air Force Two for eight years. Now I have to take off my shoes to get on an airplane," he said.

For his part, Bush is getting help on the campaign trail from the man known as "America's mayor" — Rudy Giuliani (search). The former mayor of New York was planning to stump for the president in the battleground state of Colorado.

Bush's focus on the War on Terror includes a new television ad, debuting Monday, that closely tracks the president's remarks. With Giuliani by his side, Bush accuses Kerry of not having what it takes to fight the anti-terror battle.

Also, later this week, Bush will be joined in Ohio by Giuliani and California Gov. Arnold Schwarzenegger (search). The Bush camp has retreated in some states, such as Maine and New Hampshire; aides said it's in part because they're sure of a Bush win there.

FOX News' Liza Porteus and The Associated Press contributed to this report.