Phoenix ? Democratic presidential hopefuls focused fire on Wesley Clark 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 and Sens. John Kerry, Joe Lieberman and John Edwards took turns criticizing Clark, saying he was speaking warmly of Bush as recently as 2001, and more recently switched positions to oppose 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, primed to attack 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.”

Clark — who voted for Republicans Richard Nixon, Ronald Reagan and George H. Bush for the White House — labored to fend off the criticism.

“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.

Democratic Presidential Candidates, from left, Rep. Dennis Kucinich, D-Ohio, former Army Gen. Wesley Clark and Sen. Joe Lieberman, D-Ct., take part in the third of six debates between September and December organized by the Democratic National Committee. Thursday night's debate was in Phoenix.