"Barack Obama represents America's future, and you've got to be there for him next Tuesday," Clinton, with Obama at his side, said to the cheers of a partisan crowd.
Heaping praise on President Bush's predecessor, Obama said of Clinton: "In case all of you forgot, this is what it's like to have a great president."
Obama even prodded the crowd to cheer more, saying "Bill Clinton. Give it up!" And there was Clinton, laughing with gusto every time Obama jokingly mocked rival.
The joint appearance of the future president and perhaps the next one was the first of the campaign. It capped one of the most ambitious days of Obama's White House run, including a 30-minute prime-time infomercial in which he tried to seal the deal with voters.
It wasn't so long ago that Clinton, still a giant of his party, was publicly criticizing Obama as untested and unready for the job of president. His wife, Hillary Rodham Clinton, engaged in a grueling and ultimately losing battle with Obama for the party's nomination.
The two men later smoothed over matters. And lately, Hillary Clinton has been out campaigning for Obama. Wednesday it was Bill Clinton's time, in his element.
He clasped Obama's hand and held it high when the men came on stage. Clinton made a methodical case for Obama, describing him as a strong thinker with smart policies.
In one of his testimonials, he praised Obama for seeking the advice of experts - including him and his wife - on how to handle the country's financial crisis before acting.
"Folks, we can't fool with this," Clinton said. "Our country is hanging in the balance. And we have so much promise and so much peril. This man should be our president."
Obama said of the two Clintons: "I am proud to call them my friends."
Through the day, in two states, Obama unleashed a bleak portrayal of a McCain presidency and told a national TV audience that "the time for change has come."
Ahead in the polls, flush with cash and blanketing himself all over television, Obama said he is counting down the days but not letting up. The election looms on Tuesday.
During a, Obama addressed television audiences on three broadcast networks for 30 minutes, reinforcing a message he's spent months on the campaign trail honing.
"Ronald Reagan had 'morning in America,' but this 30-minute infomercial had the feel of 'mid-morning in America,' said CBSNews.com senior political editor Vaughn Ververs. "Obama's message of change and hope is a powerful one and the primary reason he is clear front-runner in this election. As the examples his campaign chose to highlight in their made-for-Hollywood ad illustrated, however, the message runs up against a harsh reality. It will be up to voters to decide whether he can deliver on the promises."
At the end of the broadcast, cameras cut live to him appearing at a rally in Sunrise, Fla., where 20,000 packed a hockey arena all the way to the nosebleed seats.
"In six days, we can come together as one nation, and one people," Obama said.
During the primary race, Bill Clinton said Obama's opposition to the Iraq war was a "fairy tale" and raised questions about whether the first-term Illinois senator had enough experience.
His remarks angered some black leaders who felt Clinton was dismissing Obama's historic bid, as when he compared Obama's win in South Carolina to victories by civil rights activist Jesse Jackson there in the 1980s. Clinton fumed in response that Obama's campaign "played the race card on me."
Bill Clinton played such an aggressive role in his wife's campaign that during one debate, Obama snapped at Hillary Clinton, "I can't tell who I'm running against sometimes."
Back on the trail Wednesday, in rallies in North Carolina and Florida, Obama sharpened his tone in responding to McCain's charges of socialism.
He accused his Republican rival of resorting to desperate tactics.
"I don't know what's next," Obama said. "By the end of the week, he'll be accusing me of being a secret communist because I shared my toys in kindergarten."
Obama warned voters that if McCain is elected "100 million Americans will not get a tax cut. ... At least 20 million Americans risk losing their employer health insurance. ... We'll have another president who wants to privatize part of your Social Security."
The day was signature Obama, riding momentum.
He led three rousing rallies. He reached out to huge numbers of television viewers with the informercial and taped a segment on "The Daily Show," Comedy Central's popular late-night show.
An analysis by The Associated Press indicated he had pulled ahead in enough states to win the 270 electoral votes he needs to gain the White House - with states to spare.
All the while, McCain campaigned aggressively in Florida. He welcomed the fight and vowed to win it, defying odds that seem huge.
Obama turned to ridicule to rebut McCain's daily references to Obama's encounter with Joe the Plumber. Obama had told the Ohio plumber that he wanted to "spread the wealth around" by boosting taxes on wealthier people to finance a middle class tax cut.
McCain said that amounts to socialism. Obama said McCain was down to empty name-calling.
"Whether you are Suzy the student, or Nancy the nurse, or Tina the teacher, or Carl the construction worker, if my opponent is elected, you will be worse off four years from now than you are today," Obama said. "Let's cut through the negative ads and the phony attacks."