Asked in the debate's opening moments about favorable comments he made about Mr. Bush as recently as 2001, Clark had a ready reply.
"I am pro-choice, I am pro-affirmative action, I'm pro-environment, pro-health," he said. "That's why I'm proud to be a Democrat."
For the most part, Clark's nine rivals avoided criticizing him throughout the two-hour debate at New York's Pace University — but not so one another.
Sen. John Kerry of Massachusetts seemed eager for combat, criticizing former Vermont Gov. Howard Dean for favoring a repeal of all of Mr. Bush's tax cuts to finance health care expansion and other programs. It is "absolutely wrong" to propose eliminating all cuts, said Kerry, who favors scaling back tax cuts for the wealthy while maintaining them for lower and middle income Americans.
Dean, ahead of his fellow New Englander in the latest poll in advance of the New Hampshire primary, picked up that challenge quickly.
"This is exactly why the budget is so far out of balance. Washington politicians promising everything," he said. "We cannot win as Democrats" that way, he chastised Kerry.
"Tell the truth," he prodded the Massachusetts senator.
Dean said that among the rivals, only he and Sen. Bob Graham of Florida — also a former governor — had ever balanced budgets. With Graham's campaign in financial trouble, that remark amounted to an appeal to the Floridian's supporters to give his own economic credentials a look.
More than an hour into the debate, Rep. Dick Gephardt of Missouri saw an opening to attack Dean.
He assailed the former governor for having criticized Medicare in the past, and said that in the mid-1990s, Dean spoke favorably of some of Republican Newt Gingrich's proposals for Medicare.
At the time, Gephardt said, he was the Democratic leader in the House, leading the fight against plans promoted by the former Speaker and champion of the GOP revolution in Congress.
Referring to Dean's self-description as the candidate of the Democratic wing of the Democratic Party, Gephardt said, "I think you're just winging it."
"That is flat-out false," Dean said of the attack. He added, "Nobody up here deserves to be compared to Newt Gingrich."
The debate was the latest in a series of candidate summits sponsored by the Democratic Party, and billed in advance as a clash over economic issues.
Asked about President Bush's request for $87 billion in increased funding for Iraq and Afghanistan, only Rep. Dennis Kucinich of Ohio and Al Sharpton said flatly they would oppose the funds.
Sen. Joe Lieberman of Connecticut said, "we have no choice but to finance this program" to protect 140,000 American troops in Iraq and bring them home.
Sen. John Edwards of North Carolina said, "I would vote for what is necessary to support the troops."
Gephardt said Congress needs more information from the administration before voting on Mr. Bush's request and said it can't be assumed that Republicans would vote for the plan.
In a jab at the president, Gephardt added, "It's incomprehensible to me that he can go to the U.N." seeking help from other nations and "come away empty-handed."
Asked whether they would pledge not to raise taxes, Graham and Lieberman both declined.
Clark, who has only just begun sketching out a domestic agenda, said he was determined to attack the ballooning federal deficit. He said he was prepared to "put all government programs on the table, including the military programs."
Asked his own view about Mr. Bush's request for additional funding for Iraq, he sought to turn his relative political inexperience into an asset.
"If I've learned one thing in my nine days of politics, you better be careful with hypothetical questions," said the retired general.
The debate came in a campaign intensifying — about four months in advance of voting in Iowa's caucus and New Hampshire's primary.
Inevitably, the field seemed to be sorting itself out along financial lines.
With the next fund-raising reporting period a few days away, campaign officials said Graham is experiencing difficulties that have put his campaign in peril.
On the other hand, Dean — the surprise of the early pre-primary campaign — is expected to shatter party fund-raising records for a single three-month quarter.
Clark's entry into the race posed the largest threat to Dean — the man who has vaulted ahead of the field in fund raising and pre-primary polling in several states.
The little-known Clark grabbed the top spot in some national polls, but he is far behind his rivals in key early voting states. Public polls and private campaign surveys put him in single digits in Iowa and New Hampshire, though he may be faring better in South Carolina.
He has quickly built a solid team of veterans from the Clinton-Gore administration. His debate guests included Rep. Rahm Emanuel, D-Ill., a former Clinton White House aide.