"I'm very proud and honored to endorse Howard Dean as the next president of the United States," Gore said in an appearance with Dean in the Harlem section of New York City.
"Howard Dean really is the only candidate who has been able to inspire at the grassroots level, all over this country, the kind of action and enthusiasm for democracy and for change and transformation of America that we need in this country. We need to remake the Democratic Party, we need to remake America. We need to take it back on behalf of the people of the country."
Gore, who won the popular vote but lost the electoral vote in the disputed 2000 election, traveled with the former Vermont governor to Iowa Tuesday for a formal endorsement.
There, Gore addressed the fear of some Democrats that Dean's blunt-speaking ways will cause political trouble for the ticket.
"I think people realize that he sometimes speaks off the cuff, but they realize also that this is a result of him speaking from the heart. And he doesn't hold back," he said.
A senior Dean campaign official said Dean and Gore had a scheduled call on Friday. Dean thought the call would be about foreign policy, since he sought Gore's input on that topic. Gore told him that he'd decided to endorse; Dean's campaign said it came as a surprise.
"I actually never asked the vice president for his endorsement, I knew he would make that decision on his own and that he knew how important it was," Dean said in Iowa.
Gore also hinted that the other eight Democratic presidential contenders should drop out for the good of the party.
"Democracy is a team sport … I want to do everything I can to convince you to get behind Howard Dean and make this a successful campaign as a group … all of us need to get behind the strongest candidate," he said.
Dean said he appreciates the "strong, steady hand" Gore is lending to the party.
Gore and Dean appeared in Harlem before flying to Cedar Rapids, Iowa, where Dean is locked in a tight race with Missouri Rep. Richard Gephardt in the Jan. 19 Democratic caucuses.
Dean will then fly to New Hampshire in time for the final Democratic debate of the year.
While Dean leads in polls in New Hampshire and Iowa, the race has not taken shape beyond the initial voting states, and Gore's endorsement will not erase concerns about Dean's lack of foreign policy experience and campaign missteps.
The Gore Factor
The coveted endorsement is a victory for a candidate whose anti-war, anti-establishment candidacy has given pause to party leaders and key constituencies, several Democratic strategists said.
"What this says is that all these Washington insiders who have been gnashing their teeth, wringing their hands and clinging to their cocktail cups can relax now. Dean's been knighted by the ultimate insider," said Democratic consultant Dean Strother. "It's game, set and match. It's over."
Added Democratic strategist Steve Jarding: "This sends a clear signal that Dean is bringing together two major forces — Democratic insiders and outsiders. Gore is the ultimate insider," Jarding said, adding that Dean can still be beaten "but it just got a ton harder."
Sen. Chuck Schumer, D-N.Y., told Fox News that, "I have long since given up on prognosticating" election outcomes. "How it will play? Your guess is as good as mine."
Other Democrats and pundits offered more cautious appraisals.
"I don't know that it changes the playing field that much," Craig Smith, Sen. Joseph Lieberman's campaign manager, told Fox News. "We'll wait till the voters have a say-so in this and I'll trust the future of my country to those guys … whether he [Dean] can beat George Bush is a big question."
"It's December — there's so many ways Howard Dean can still screw this up," added Ellis Henican, a Newsday columnist and Fox News political contributor.
"Long term, I don't know what the impact will be," added Senate Majority Leader Bill Frist of Tennessee.
Lieberman, the Democratic presidential contender from Connecticut who was Gore's vice presidential pick in 2000, said he was caught "completely off-guard" by the news, particularly because he believes Dean's position on the key issues are at odds with Gore's.
"I was surprised. I'm not going to talk about Gore's sense of loyalty," a jilted Lieberman told NBC. But, he added, "I'm more determined than ever to fight for what I believe is right for my party and my country."
Gore is widely popular among key primary voters due in part to the widespread belief among Democratic activists that the election was taken from him. His approval bolsters Dean's case that he represents more than an Internet-driven outsider relying on the support of largely white, upscale voters.
Democratic strategist Jenny Backus said Gore will help Dean gain access to "some key constituencies, African-Americans and women and organized labor, and in Iowa."
Analysts noted that Gore's uneven performance in 2000 alienated many party leaders, giving his endorsement limited appeal, and they predicted an anti-Dean movement will eventually form behind one of his eight rivals.
In 1998, Dean considered challenging Gore for the Democratic nomination in 2000, but backed away amid pressure from the vice president's office and opposition in Vermont. He quietly lobbied to be mentioned as a vice presidential candidate, but did not make Gore's short list.
The pair has differed on many key issues such as gun control. While Gore fought the National Rifle Association (search), Dean was embraced by the lobby.
The Other Eight
Other Democratic contenders noted the differences in opinion between Gore and Dean.
A Gephardt spokesman issued a statement citing the congressman's work with Gore to "pass the Clinton economic plan, pass the assault weapons ban and defend against Republican attacks on Medicare and affirmative action. On each of these issues, Howard Dean was on the wrong side."
Democratic candidate Wesley Clark (search) issued a statement touting the number of former Gore staffers working on his campaign.
"I respect Al Gore. I worked with him in the Senate, and I endorsed him early in his hard-fought campaign for the presidency four years ago," added Massachusetts Sen. John Kerry. "But, this election is about the future, not about the past."
Dean and Gore began having regular, monthly conversations after a Sept. 21, 2002, Gore speech, according to the senior Dean campaign official. Dean felt the speech validated and reaffirmed his own stance on the war and he called Gore to tell him. Since then, he's sought Gore's advice on a number of issues, and around late August, they spoke every 10 days or so. In early November, Dean went to Nashville, Tenn., and met with Gore for over an hour at Gore's residence.
Fox News' Carl Cameron, Liza Porteus and The Associated Press contributed to this report.