"With Joe Biden's experience and wisdom, supporting Barack Obama's proven understanding, insight and good instincts, America will have the national security leadership we need," Clinton said.
Clinton campaigned feverishly for his wife, Hillary Rodham Clinton, in her long-fought primary battle against Obama, and took her loss hard. He had not spoken out as strongly in support of Obama since he clinched the nomination in June.
But Wednesday, he was unambiguous in passing the torch of Democratic leadership to Obama.
Jabbing a finger at thousands of cheering delegates, he declared: "I want all of you who supported her to vote for Barack Obama in November."
Running just over 20 minutes, the speech by the godfather of the Democratic Party whipped thousands of delegates into an exuberant frenzy. Where a night before they had hoisted "Hillary" banners, on this night they waved American flags.
The delegates stood on their feet and roared for nearly 3½ minutes when Clinton walked on stage. The former president basked in their affection, but after several false starts at his speech, commanded: "Sit down!"
Clinton was by turns funny, nostalgic and wonkish, touching on issues like health care and pension benefits.
Clinton, ever mindful of himself, likened Obama's presidential quest to his own bid for the presidency in 1992, when "Republicans said I was too young and too inexperienced to be commander in chief."
"Sound familiar?" Clinton said. "It didn't work in 1992, because we were on the right side of history. And it won't work in 2008, because Barack Obama is on the right side of history."
He allowed that the primary campaign had generated "so much heat it increased global warming."
"In the end," he said, "my candidate didn't win. But I'm proud of the campaign she ran: She never quit on the people she stood up for, on the changes she pushed for, on the future she wants for all our children."
The former president's wide-ranging speech also attacked Republicans for an "exploding" national debt and misguided foreign policy.
Clinton's address elicited some nostalgia of its own among the delegates.
"He can still mesmerize a crowd," said Oregon delegate Sam Sappington.
Standing nearby, Lloyd Henion, who came to Denver as a Clinton delegate from Oregon, said the former president "hit a 500-foot home run. He hit all the points."
"That was as clear a message as you could get as to why Barack Obama should be president," Henion said of Bill Clinton's speech.
Clinton's challenge Wednesday night was tall, because he himself had questioned Obama's credentials.
During the primary race, the former president tried to raise doubts about whether the first-term Illinois senator had the experience to lead the country. He said Obama's opposition to the Iraq war was a "fairy tale."
Last fall, he dismissed Obama as totally unqualified.
"I mean, when is the last time we elected a president based on one year of service in the Senate before he started running?" Clinton said on "The Charlie Rose Show. "In theory, we could find someone who is a gifted television commentator and let them run."
Last winter, Clinton said that after "all the mean things" the Obama campaign had said about him, "I should be the last person to defend him. (But) if he wins this nomination, I'm going to do what I can to help him win."
Since Obama clinched the nomination in June, Clinton has seemed less than passionate about an Obama presidency, giving only lukewarm endorsements.
Clinton was departing Denver on Thursday morning, hours before Obama gives his acceptance speech.
Aides said this was standard practice for Clinton, and not a snub. Clinton did likewise at the 2000 and 2004 conventions.
