Democratic presidential hopefuls focused fire on Wesley Clark (search) in campaign debate Thursday night, deriding the retired general as a belated convert to their party -- and indecisive to boot.

"I did not vote for George Bush. I voted for Al Gore," Clark retorted in the most contentious of four debates to date in the battle for the Democratic nomination.

Former Vermont Gov. Howard Dean (search) and Sens. John Kerry (search), Joe Lieberman (search) and John Edwards (search) took turns criticizing Clark, saying he was speaking warmly of Bush as recently as 2001, and more recently switched positions on the war with Iraq.

Clark struck an above-the-fray pose at one point, insisting, "I'm not going to attack a fellow Democrat."

But even that drew a sharp response from his rivals, who took aim at the retired Army general who jumped to a lead in some national polls within days of his entry into the race in September.

"I want to say ... welcome to the Democratic presidential campaign," Lieberman said. "Look, none of us are above questioning."

After the debate, Clark said the criticism came as no surprise.

"When you're the front-runner, you have to expect that," he said in an interview with The Associated Press. Although he leads in national surveys, he trails his rivals in state polls, including a recent New Hampshire survey.

With the pace of the campaign quickening, the Democrats traded jabs over economic policy as well.

Gephardt told a questioner in the debate audience he favors repealing Bush's tax cuts in their entirety, and insisted that would not result in an increase in her taxes.

But Kerry, who favors retaining Bush's tax cuts only for middle-income individuals, said, "You're going to pay more tax" if all cuts are repealed.

The field of Democratic contenders -- shrunken by one with Florida Sen. Bob Graham's withdrawal from the race -- met onstage at the Orpheum Theater in Phoenix, capital of a state that holds an early primary on Feb. 3.

For the first half of the debate, the candidates sat on tall chairs in front of identical lecterns. A cable network sponsored the debate, and Judy Woodruff, a network anchor, served as moderator.

The format switched halfway through. The lecterns disappeared, the men shed their suit jackets and fielded questions from the audience -- the first time in any of the debates that the candidates have responded to questions from men and women whose votes will prove decisive in the early primary states.

When they weren't sparring with one another, Democrats took time to heap fresh criticism on Bush's postwar policy in Iraq, faulting him for failing to win significant help from other countries.

"You remember on your report card you had your English grade, your history grade and then it said, plays well together? He flunked that part," jabbed Gephardt of Missouri.

Former Sen. Carol Moseley Braun of Illinois made a similar point, saying, "I think we have to work well with others and begin to bring our troops home with honor."

Clark labored to fend off the criticism from the early moments of the debate. "I would never have voted for war. The war was an unnecessary war and it's been a huge strategic mistake for the country," he said.

But Dean said that exactly one year ago, Clark had advised a Democratic congressional candidate in New Hampshire to vote for legislation authorizing the war in Iraq -- a war the former general now criticizes sharply.

Lieberman, a supporter of the conflict, jabbed at Dean and Clark simultaneously. In a backhanded compliment, he said Dean had been steadfast in his opposition to the war.

By contrast, he criticized Clark for what he called a history of inconsistency on Iraq. He said Democrats need a candidate who can "reach a conclusion and stick to it."

Kerry said that despite Clark's declarations, the former Army general "did say he would vote for the resolution" approving the war. He also said Clark had praised Bush at a Republican fund-raiser last year -- at a time he said the Bush administration had already won tax cuts for the rich from Congress and was trying to tap into the Arctic National Wildlife Refuge in Alaska for oil.

Edwards spoke dismissively of Clark, saying that he opposed Bush from the start -- even "when some on this stage had hope for" him.

"I could still have hope in early 2001 that this administration would learn its lessons, as most administrations do," said the retired general, who attended a GOP fund-raiser that year.

"Americans believed they had selected a compassionate conservative," he added. "Instead we had a guy who has deepened the deficits. He's taken us recklessly into war. And he's been a radical, not a compassionate conservative."

Clark also criticized his Washington-based rivals for failing to take action against Bush's foreign policy. He said North Korea and Iran are accelerating their nuclear weapons development in reaction to the administration's "pre-emptive doctrine" and the Democrats in Congress are doing nothing to stop it.

Dean accused several rivals of giving Bush "a blank check to go to war in Iraq" by voting for or voicing support for a congressional resolution last year.

But Dean also said he would support Bush's request for $87 billion to maintain the troops stationed in Iraq and help rebuild the country.

That, in turn, drew a challenge from Ohio Rep. Dennis Kucinich, who said the troops should be brought home because "they are targets" for terrorists in the land that Saddam Hussein once ruled.

In a bit of political jujitsu, Kerry's backstage aides fed material to Woodruff near the end of the debate alleging that Dean had once tried to deny prescription drug benefits to elderly Vermonters.

Woodruff confronted the former governor with the information. "That's silly," he said, adding he had informed the legislature at the time that if it didn't raise cigarette taxes, there wouldn't be enough money to pay for the benefit. Lawmakers relented, he added.