Former president Bill Clinton, right, making his first appearance since his heart surgery joins Democratic presidential candidate Sen. John F. Kerry, D-Mass, at a campaign rally in Philadelphia Monday, Oct. 25, 2004.(Xinhua/AFP Photo)

Former US president Bill Clinton campaigned for Democratic Senator John Kerry on Monday, seven weeks after undergoing heart surgery, saying Kerry would make America "the Comeback Country."

"From time to time, I have been called the Comeback Kid. In eight days, John Kerry is going to make America the comeback country," Clinton said in a joint rally with Kerry in Philadelphia, Pennsylvania.

Kerry was struggling to hold on to his slim lead in Pennsylvania, one of a few swing states on which he and President George W. Bush are relentlessly focusing in the last days of the presidential race.

The Kerry campaign hoped Clinton's appearance would help energize the Democratic base and also attract undecided voters by reminding them of the prosperity they have had during Clinton's presidency in the 90s.

Speaking in a slightly hoarse but strong voice, Clinton assaulted the domestic and foreign policies of the Bush administration, saying Bush's plan for the next four years would be "more of the same."

"John Kerry's got a better plan," Clinton said. "We can do better and in eight days we're going to do better with President John Kerry."

The drama of a popular former president emerging only weeks after quadruple bypass surgery reflected the intensity of the race. Polls showed the election is too close to call.

"Senator Kerry asked me to do it, and I want to do it," Clinton told ABC's program "Good Morning America" broadcast Monday. "Because it's close and because I think it's important and because the differences between the two candidates and the courses they'll pursue in the next four years are so profound."

Clinton headed to a rally in Miami, Florida, another battleground state, later on the day. he also has an event scheduled for Broward County, Florida, on Tuesday.

A Wall Street Journal/NBC News poll last week showed Clinton with a 48 percent positive rating and a 38 percent negative rating. His positive rating was even higher among independents, swing and undecided voters.