DURHAM, N.H. (Reuters) - The Democratic presidential contenders questioned on Tuesday whether Howard Dean could win the White House in November, contending the race was far from over despite Al Gore's endorsement of Dean.

But at a sedate debate in New Hampshire, site of the campaign's first key primary on Jan. 27, the Democrats battling for the right to challenge President Bush in 2004 rarely put Dean on the hot seat, instead touting their own electability and focusing their attacks on Bush's policies in Iraq.

The endorsement of Dean earlier on Tuesday by Gore, the former vice president and loser to Bush of the bitterly contested 2000 election, put the former Vermont governor in a commanding position but not surprisingly failed to convince any of his eight rivals his nomination was inevitable.

"This race is not over until votes have been cast and counted," said Massachusetts Sen. John Kerry, whose early lead in the New Hampshire polls has vanished as Dean surged ahead by a large double-digit margin.

Gore's endorsement helped feed the momentum for Dean, the former long shot who recently won the backing of two influential labor unions and has seen a flurry of opinion polls showing him widening his leads in New Hampshire and the early caucus state of Iowa.

It also was a slap in the face for Connecticut Sen. Joseph Lieberman, Gore's running mate in 2000 who had promised he would not run for president if Gore did.

Lieberman said Democrats would decide in 2004 whether the party would expand on former Democratic President Bill Clinton's efforts to build a strong defense, create more jobs and cut taxes on the middle class.

"Howard Dean -- and now Al Gore, I guess -- are on the wrong side of each of those issues," Lieberman said. "We're only going to defeat George Bush if we have an independent-minded, center-out Democrat."

'BOSSISM'

Civil rights activist Al Sharpton accused Gore of "bossism" in trying to dictate who Democrats should nominate. "Al Gore -- no Democrat should shut us up today. Let the people decide on the nominee. Bossism shouldn't happen," he said.

Dean said his rivals should focus on attacking him, not Gore.

"If you guys are upset that Al Gore is endorsing me, attack me, don't attack Al Gore," he said. "Al Gore worked too hard in 2000 to lose that election, when he really didn't lose the election."

Moderator Ted Koppel of ABC News opened the debate by asking the candidates to raise their hands if they thought Dean could beat Bush -- only Dean did.

The only other topic explored at length in the debate was the war in Iraq, with Democrats saying Bush had failed to plan for the country's occupation or build the international support needed to ease the U.S. burden there.

"With this administration in office, we could be in Iraq for the next 50 years," said retired Gen. Wesley Clark. "They can't fix the region because they don't have a diplomacy that will bring people together and work with them."

Bush's Iraq policies were creating a possible "clash of civilization of a radical state of Islam against the world," Kerry said. "If we're not successful in Iraq, we will make life worse in Pakistan, worse in Saudi Arabia, worse in Egypt."

When Dean said the "tragedy" of Iraq was that the United States was stuck there, possibly for years, until a representative Iraq government could take control, Ohio Rep. Dennis Kucinich disputed the idea.