Early and often, on Iraq, Iran and electability, Hillary Rodham Clinton was sharply criticized by her rivals during a Democratic presidential debate Tuesday night at Drexel University.

This encounter was much the candidates' most contentious of the year, with the front-runner taking repeated verbal shots, particularly from Barack Obama and John Edwards.

Obama, the senator from Illinois, accused Clinton of changing her positions on the North American Free Trade Agreement, the Iraq War, and the definition of torture.

"That may be politically savvy," Obama said, "but I don't think it offers the clear contrasts [with the Republicans] we need."

Edwards, the party's former vice presidential nominee, depicted Clinton as the embodiment of the political status quo, noting the amounts of money she's taken from interest groups.

"Will she be the person who brings about change in this this country?" asked Edwards, whose attacks were the most persistent. "I believe in Santa Claus. I believe in the tooth fairy. But I don't think that's going to happen."

While Clinton defended herself at times, she seemed unrattled by the attacks. Mostly, she was content to restate her positions and to scoff at the notion that her election would not represent significant change.

"I have been standing against the Republicans, George Bush and Dick Cheney," she said, "and I will continue to do so, and I think Democrats know that."

One question which her rivals were eager to discuss when given the change was whether Clinton can win a general election.

Polls show that over 40 percent of all voters say they have ruled out voting for her in November. At the same time, she is winning hypothetical matchups with the various Republicans nominees, most of whom talk of her as if she were already nominated.

"Part of the reasons Republicans are so obsessed with you is that's a fight they're very comfortable having," said Obama, who had announced in advance his intention to be more aggressive. "What we don't need is another eight years of bickering."

Edwards chimed in, saying telling Clinton that the Republicans "want to run again you."

Finally, New Mexico Gov. Bill Richardson tried to put a stop to the sniping, even as he reminded viewers that governors like himself, not senators like Clinton, get elected president.

"I'm hearing this holier than thou attitude toward Senator Clinton and it's bothering me," he said, "because it's pretty close to personal attacks we don't need."

Clinton is getting nearly 50 percent of the Democratic vote in some national polls and is leading most of the key early states, although she faces a tough fight with Obama and Edwards in Iowa, site of the first-in-the-nation caucuses on Jan. 3.

For that reason, her rivals looked for every opportunity to weaken her, including discussion of the resolution enacted in the Senate last month labeling Iran's Revolutionary Guard a terrorist organization.

Clinton voted for it. Two other candidates, Senators Joe Biden of Delaware and Christopher Dodd of Connecticut, voted against it. All of the others said that supporting it was a mistake.

Biden said that the resolution had emboldened the Bush administration in moving toward a military confrontation with Iran, raised the price of oil worldwide, and created political instability in Pakistan and Afghanistan.

"If nothing else happens, this was bad policy," Biden said. "All it has done is hurt us."

Said Dodd: "I believe this issue is going to come back to haunt us." Added U.S. Rep. Dennis Kucinich of Ohio, "When you say all options are on the table, you are licensing President Bush" to move toward war.

Edwards suggested that Clinton's action was naive at best. "The way you put pressure on this administration is you step up to them and say no," he said. "You give this president an inch and he'll take a mile."

As for herself, Clinton said that she wanted to make sure everyone understood her position on Iran. "I am against a rush to war," she said. "I also am not in favor of doing nothing."

The Senate resolution, she said, called for vigorous diplomacy, including economic sanctions, which she called the right way to try to prevent Iran from acquiring nuclear weapons.

Clinton took heat on the war in Iraq as well, even as she reiterated her measured plan to extricate the United States from that conflict. That plan has not satisfied some voters in the party's anti-war base.

"I will begin to bring our troops home as soon as I'm president," she said.

Obama, who described Clinton as having been supported the war before she opposed it, said that she was not the right person to undo the Bush policies. The key, he said, is having a president "who has not been one of the co-authors of this engagement in Iraq."

Edwards accused her to wanting to leave combat troops behind to wage combat missions and pointed to her unwillingness to set a timetable for complete withdrawal.

"You have choices, very clear choices," Edwards said. "I will get the troops out in my first year."

The field also pounced on the senator from New York when she appeared to endorse the idea of states' giving drivers' licenses to undocumented immigrants, then back away from it.

Not all of the conversation centered on Clinton. The candidates were asked about education, energy policy, natural disasters, immigration, health care, tax policy and Social Security.

Perhaps the best line of the night - in terms of the reception from the pro-Democratic crowd at Drexel's Main Building Auditorium - came from Biden, who has made no secret of his contempt for the idea that Republican Rudy Giuliani might get elected president.

"All he says is a noun and a verb and 9/11; there's nothing else," Biden said. "He is genuinely not qualified to be president."

Missing from the stage was former Sen. Mike Gravel, who was kept away by MSNBC, which televised the event, on the grounds that he did not meet minimal standards of what it means to be a candidate.

Despite the big-city setting, no special attention was given to urban issues by the questioners, Brian Williams and Tim Russert of NBC News.

Contact senior writer Larry Eichel at 215-854-2415 or leichel@phillynews.com.