Democratic presidential hopeful former Sen. John Edwards, D-N.C., left, speaks during a debate as Sen. Hillary Rodham Clinton, D-N.Y., and Sen. Barack Obama, D-Ill., listen Tuesday at Drexel University in Philadelphia.

Philadelphia ? Democrats Barack Obama and John Edwards sharply challenged Sen. Hillary Rodham Clinton’s candor, consistency and judgment Tuesday in a televised debate that underscored her front-runner status two months before the first presidential primary votes.

Obama, the Illinois senator, began immediately, saying Clinton has changed her positions on the North American Free Trade Agreement, torture policies and the Iraq war. Leadership, he said, does not mean “changing positions whenever it’s politically convenient.”

Edwards, the former North Carolina senator, was even sharper at times, saying Clinton “defends a broken system that’s corrupt in Washington, D.C.” He stood by his earlier claim that she has engaged in “doubletalk.”

Clinton, standing between the two men, largely shrugged off the remarks and defended her positions. She has been the focus of Republican candidates’ “conversations and consternation,” she said, because she is leading in the polls.

She said she has specific plans on Social Security, diplomacy and health care. “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.”

But she avoided direct answers to several questions. The New York senator wouldn’t say how she would address the fiscal crisis threatening Social Security, she declined to pledge whether she would stop Iran from developing a nuclear weapon or say whether she supports giving driver’s licenses to illegal immigrants. Rather, she tried to turn every issue into an argument against President Bush.

It was the Democrats’ first debate in a month, and during that time Clinton has solidified her front-runner position, gaining in polls, taking the lead in fundraising and dominating the agenda. The Iowa caucuses are scheduled for Jan. 3, and the New Hampshire primary could be even earlier.

Clinton defended her Senate vote in favor of designating Iran’s Revolutionary Guard as a terrorist group. Obama, Edwards and others have said Bush could interpret the measure as congressional approval for a military attack.

Edwards caustically challenged Clinton’s claim that she stands up to the Bush administration. “So the way to do that is to vote yes on a resolution that looks like it was written literally by the neocons?” he said.

“In my view, rushing to war – we should not be doing that – but we shouldn’t be doing nothing,” Clinton said. “And that means we should not let them acquire nuclear weapons, and the best way to prevent that is a full-court press on the diplomatic front.”

Clinton also was the main focus during a discussion of the Iraq war. Again, Edwards leveled the toughest charges against the New York senator.

“If you believe that combat missions should be continued in Iraq” without a timetable for withdrawal, Edwards said, “then Senator Clinton is your candidate.” Edwards vowed to have all combat troops out of Iraq “in my first year in office.”

Clinton replied forcefully, saying, “I stand for ending the war in Iraq, bringing our troops home.” She added, however, that “it is going to take time,” and some troops must remain to fight al-Qaida in Iraq.

“I don’t know how you pursue al-Qaida without engaging them in combat,” she said.

Edwards, drawing a link between Iraq and Iran, pressed on. “What I worry about is, if Bush invades Iran six months from now, I mean, are we going to hear: ‘If only I had known then what I know now?'” He was alluding to comments Clinton has made about her 2002 vote to authorize military action against Saddam Hussein.