CLEVELAND—With March 4 looming as either the death or rebirth of her campaign, Sen. Hillary Clinton tonight engaged in a combative debate against Sen. Barack Obama, both drawing sharp distinctions to gain advantage in must-win Ohio.

Desperately needing a strong debate performance to stem Obama’s momentum after consecutive victories in 11 states, Clinton came out aggressively, castigating Obama for distorting her stands on health care and the North American Free Trade Agreement in mailings to Ohio Democratic voters.

"What I find regrettable is that in Sen. Obama’s mailing that he has sent out across Ohio, it is almost as though the health insurance companies and the Republicans wrote it," Clinton said.

Front-runner Obama parried the attacks, avoiding a damaging misstatement, illustrating his growing skill as a debater in the 20 ^th and perhaps defining debate of the Democratic race.

"Sen. Clinton repeatedly claims that I don’t stand for universal health care," Obama said. "And, you know, for Sen. Clinton to say that I think is simply not accurate."

From the start, the 90-minute debate was combative. The first hour was bereft of the light-heartedness and occasional warmth illustrated in previous debates between the two. Instead, they frequently talked over each other under pointed questioning from NBC’s Brian Williams and Tim Russert.

The debate at Cleveland State University before a an audience of 1,600 whose relative quietness reflected the somber tone of the event was especially critical for Clinton, who in the judgment of her husband, former President Bill Clinton, needs wins in Ohio and Texas on March 4 to continue a viable campaign. Tonight, Ohio Democratic Chairman Chris Redfern, officially neutral in the race, said Clinton "needs a double-digit win in Ohio" against the surging Obama.

The sharpest exchanges came early as Clinton and Obama detailed their plans on health care, repeatedly saying the other was using mischaracterizations.

Clinton pressed her case that Obama’s health care plan would leave millions of Americans uninsured, while her own universal plan would require everyone to have health insurance, including the 47 million Americans who do not have it now.

"Every expert as said that anybody who wants health care under my plan will be able to obtain it," Obama countered.

The candidates also had sharp exchanges on the North American Free Trade Agreement, the trade deal pushed through Congress by Clinton’s husband, and which Obama says is partly responsible for Ohio’s loss of 257,600 manufacturing jobs since 2000.

Clinton, who was on record as supporting NAFTA during her husband’s administration, said it is "flawed" and both candidates want NAFTA renegotiated with Mexico to beef up labor and environmental standards. Clinton also has called for a "timeout" on new trade agreements.

Asked if they were willing to opt out of NAFTA within six months of becoming president, both candidates said they would consider it.

"I will say we will opt out of NAFTA unless we renegotiate it and we renegotiate it on terms that are favorable to all of America," Clinton said.

"I think we should use the hammer of a potential opt-out as leverage to ensure that we actually get labor and environmental standards that are enforced," Obama said.

Both candidates have advocated a phased withdrawal of U.S. troops from Iraq, but when asked if the would "re-invade" Iraq if al Qaeda established it as a stronghold after the troops are gone, the candidates split.

Clinton called the question hypothetical and said she would work with the Iraqi government to keep al Qaeda from using Iraq as a staging base for attacks. Obama indicated it might be necessary for troops to go back.

"Now, I always reserve the right for the president — as commander-in-chief, I will always reserve the right to make sure that we are looking out for American interests," Obama said. "And if al Qaeda is forming a base in Iraq, then we will have to act in a way that secures the American homeland and our interests abroad."

At one point, Clinton hinted that the questioning in debates had been especially tough on her, and she drew a reference to a recent Saturday Night Live skit about reporters going easy on Obama.

"I just point out that, in the last several debates, I seem to get the first question all the time? And I don't mind. You know, I'll be happy to field them, but I do find it curious. And if anybody saw Saturday Night Live, you know, maybe we should ask Barack if he's comfortable and needs another pillow."

The candidates and their surrogates aren’t wasting any time after the debate to resume campaigning in Ohio.

Obama has a rally scheduled Wednesday at St. John Arena at Ohio State University in Columbus, while Clinton has an "economic solutions summit" Wednesday in Zanesville with participants including former Sen. John Glenn, Gov. Ted Strickland, New Jersey Gov. Jon Corzine and even Florine Mark of Weight Watchers.

Clinton also scheduled a rally in St. Clairsville Wednesday and has other stops planned Thursday in Appalachian Ohio.

jhallett@dispatch.com