The early endorsement by Al Gore (search) of Democratic presidential front-runner Howard Dean (search) has shown real cracks in the Democratic Party, where candidates rejected by Gore are trying to make up for the loss with stinging attacks on Dean.

Party notables have also expressed their surprise, and in some cases, disappointment with Gore for taking such an early position.

"I remember back in December of 1991, when my husband was, I don't think, above 4 percent in the polls. I remember all the way through the months of the primaries and the caucuses there was a hard-fought battle ... so I want to see how the process plays out," said New York Sen. Hillary Clinton, who dismissed the idea of a front-runner and has said she would not support a candidate in the primary. 

At the year's eighth and final debate Tuesday night in New Hampshire — just six weeks from the first presidential primary on Jan. 19 in Iowa, the candidates issued stiff criticism of the former Vermont governor, Gore's endorsement notwithstanding.

"This race is not over," declared Sen. John Kerry (search) of Massachusetts as the candidates gathered in this first-in-the-nation primary state for the debate.

Joe Lieberman (search), Gore's spurned 2000 running mate, asserted that "my chances have actually increased today." The Connecticut senator said people had stopped him in the airport to express outrage over Gore's backing of Dean.

For his part, Dean told the others: "Attack me. Don't attack Al Gore. I don't think he deserves to be attacked by anybody up here."

Clearly Gore's endorsement overshadowed the debate. The comments on Gore's stunning decision was precipitated when one of the debate's moderators, ABC's Ted Koppel, invited the field of nine candidates to "raise your hand if you believe that Gov. Dean can beat George Bush."

Only one, Dean, raised his hand.

Gore's blockbuster endorsement Tuesday began with an announcement in the Harlem section of New York, followed by a trip to Iowa before heading to New Hampshire.

"I'm very proud and honored to endorse Howard Dean to be the next president of the United States," Gore, the consummate establishment insider and 2000 presidential candidate, said of the insurgent outsider.

Gore said Dean alone has created the kind of political buzz in the party's liberal base that Democrats need to win.

"Howard Dean is the only candidate who has been able to inspire at the grassroots level all over this country the kind of passion and enthusiasm for democracy and change and transformation of America that we need in this country," Gore said.

Polls show that Gore may be rolling with the pack. While he has steadily held the lead in statewide polls, nationally Dean has not ranked in the top tier of presidential candidates — until now.

According to a new Gallup poll, 25 percent of registered Democrats across the country support Dean, compared with 17 percent who support retired Gen. Wesley Clark (search). Clark has topped every Gallup poll since he entered the race in September, but while his popularity has steadily declined, Dean's has nearly doubled.

For his part, Dean said he was ecstatic and surprised to learn of Gore's support, and he thinks it will help his campaign.

"It helps us enormously. We have been seen as the insurgent campaign and we are the insurgent campaign, but the truth is, we are not going to win this campaign against George Bush unless we unite the entire Democratic Party, and this is a big step in doing that," Dean said.

Gore suggested Tuesday that Dean's critics, rather than trying to beat him, should join him.

"We don't have the luxury of fighting among ourselves to the point where we seriously damage our ability to win on behalf of the American people," he said.

But Gore's enthusiasm for Dean is not universally shared, particularly among the candidates, their supporters and the undecided.

"It doesn't really sway me," said Susan Barnes, 41, a Democrat who voted for Gore in 2000. "What really does it for me is where [the candidates] stand on the important issues."

"Most voters have seen a lot from these candidates, so I'm not sure any endorsement is going to make a difference," said Andrew Smith, director of the University of New Hampshire Survey Center (search).

Gore's 2000 presidential running mate and current candidate Lieberman also expressed his dismay at Gore's decision, suggesting the former vice president has abandoned the winning centrist strategy that he helped lead in the Clinton administration.

"I was surprised about the decision, I was surprised that Al Gore didn't notify me before I learned about it from the media, that would have been the right thing to do. I was surprised that Al Gore would endorse the candidate who stands for so many things that Al Gore has not stood for," Lieberman said.

Sen. Edward M. Kennedy, D-Mass., who unsuccessfully sought the Democratic nomination in 1980, played down the significance of the Gore endorsement and said his support is still firmly behind Kerry, who has lost the most ground as a result of Dean's surge.

Kennedy said voters now are thinking about the holidays — not about making decisions on the future president. He said a lot is made of staff shake-ups and endorsements, but "ultimately it's going to come down to the candidates."

"I think people like to make up their own mind in the Democratic Party," he said.

For now, that's what the candidates are hoping. In politics, a month can be an epoch, as Missouri Rep. Dick Gephardt (search) learned during his 1988 bid for the presidential bid.  In December 1987, Gephardt had the support of 6 percent of Iowa voters. He ended up winning that state.

Gephardt is again banking on Iowa, spending most of his time there, and tying Dean in polls in that state. Gephardt is counting on Iowa to propel him through New Hampshire eight days later and the seven states going to the polls on Feb. 3.

One of those states is Missouri, Gephardt's home. Another is South Carolina, where North Carolina Sen. John Edwards (search) is leading. Yet another is Arizona, on which Lieberman has directed much focus.

Clark and Kerry are hoping a good showing in New Hampshire can spike their momentum. The other candidates — former Illinois Sen. Carol Moseley Braun (search), Rev. Al Sharpton (search) and Ohio Rep. Dennis Kucinich (search) are far behind.

"They have to keep focused and continue to do what they originally planned to do, but the problem is that most of these guys' original strategies haven't worked as well as Dean's," said Donnie Fowler, who ran Gore's field operations in 2000 and briefly served as Clark's campaign manager. "I think that's because they don't understand the new tools of politics and they don't understand people outside of Washington, D.C."

While some analysts say Gore's backing of Dean will not make Dean any more electable than he already was, Dean's coup — though probably unlikely to have much impact on Iowa and New Hampshire where most minds are made up —  could reassure Democratic powerbrokers elsewhere about his electability.

"What's important about it is what it symbolizes nationwide for this race. It helps insulate Dean from the electability issue. He can say, 'Al Gore's no slouch, he's not going to back a loser,'" Smith said.

Gore credited Dean with taking the right position on Iraq, saying supporters of the war resolution have essentially led the nation to the worst foreign policy mistake in two centuries. 

Gore also ripped into candidates, like Lieberman, who backed the war and argued Dean is weak on foreign policy experience.

"When I hear people who made the wrong judgment about getting us into this quagmire in Iraq stand up and say, 'Well, his position on the war proves that he doesn't have the understanding of foreign policy,' I think well, they're turning things upside down on that. He is the one that did have the good judgment," Gore told an audience in Cedar Rapids, Iowa.

"This helps position Dean as much more in the mainstream because it will help people realize that Gore was anti-war as well," said longtime Gore adviser Elaine Kamarck. "There is a pro-defense wing of the party that was anti-war."

Fox News' Carl Cameron and The Associated Press contributed to this report.