Rivals John Kerry and John Edwards exchanged jabs but no body blows in a lively presidential debate Thursday in Los Angeles.

Seated shoulder-to-shoulder at a table rather than standing at lecterns, the two leading Democratic candidates sparred over issues ranging from trade policy to electability. Both appeared to squirm when the controversial issue of gay marriage was raised.

As he has in the past, Senator Edwards of North Carolina sought to contrast his blue-collar roots with Kerry's blue-blood background. But he carefully avoided accusing Kerry of being completely out of touch.

"I'm saying he comes from a different background," said Edwards of Kerry, the front-runner. "I mean, he's a good man. He's a good candidate. He'd make a good president, and I'd be the first to say that. But we come from different places, and we present different choices."

Kerry, the junior senator from Massachusetts, countered that he received valuable exposure to other socioeconomic classes during his service in Vietnam. And he took an indirect swipe at President Bush.

"The kids I fought with were kids out of the barrios of Los Angeles, and the kids from South Central Los Angeles, and from the south side of Chicago, and South Boston and a lot of other places, because they couldn't get out of the draft," said Kerry. "They didn't know how to make those phone calls. They didn't have the ability to have a choice."

Critics charge that Bush used political connections to avoid combat in Vietnam. He instead served in the National Guard and never left the U.S.

The sharpest exchange between the rivals came on the subject of the North American Free Trade Agreement (NAFTA). For weeks, Edwards has stressed that NAFTA caused the loss of thousands of manufacturing jobs. On Thursday, Kerry accused Edwards of flip-flopping on the issue.

"This is not some academic, trade-policy, Washington issue for me," said Edwards, subtly jabbing at Kerry, who is often accused of being overly aloof. "I have seen up close what happens when mills and factories close. I saw what happened in my own hometown when the mill that my father worked in closed."

"I wasn't in the Congress when NAFTA was passed," said Edwards later. "He voted for it, but when I campaigned for the Senate, I campaigned against it."

At that statement, the normally stoic Kerry appeared flabbergasted and his reaction drew laughs from the audience filling the University of Southern California auditorium.

"Well, I am surprised, because in his major speech on the economy in Georgetown this past June, John never even mentioned trade," said Kerry. "He is quoted as saying to The New York Times that he thought NAFTA was important for our prosperity. Now he's claiming that he was against it and these other [trade] agreements."

The two candidates trod carefully in describing their positions on the subject of gay marriage while attacking President Bush for supporting a constitutional amendment that would codify marriage as strictly between a man and a woman. Earlier Thursday, former talk show host Rosie O'Donnell and longtime partner Kelli Carpenter were married in San Francisco by the city's mayor.

"This is a president who always tries to create a cultural war and seeks the lowest common denominator of American politics, because he can't come to America and talk about jobs," said Kerry.

Both Kerry and Edwards have said they believe personally that marriage should be between a man and a woman. Both indicated Thursday that individual states should determine how to handle the matter (see "Gay Marriage Issue As Complicated As It Is Controversial").

That drew a sharp rebuke from Al Sharpton, who frequently stirred the pot during the 90-minute debate.

"This is not an issue any more of just marriage," he said. "This is an issue of human rights. And I think it is dangerous to give states the right to deal with human-rights questions."

During the civil-rights struggles of the 1960s, the federal government played a key role in forcing states in the South to acknowledge the rights of blacks, a fact Sharpton has cited in the past.

Rep. Dennis Kucinich of Ohio vigorously defended his position as the party's most progressive candidate. On several occasions, he challenged his rivals by asking why they opposed a single-payer health care system similar to Canada's.

On the subject of electability, Kerry and Edwards turned into political analysts, displaying how keenly they track the exit-poll data that has been produced in the 20 states that have already voted.

Edwards contended that he stood a better chance of beating President Bush this fall because he had demonstrated greater appeal to independent and Republican voters -- especially in the South -- than Kerry.

"Nothing documents what he just said," Kerry responded, citing the number of independent votes he garnered in Iowa and the strong wins he posted in the Virginia and Tennessee primaries held earlier this month.

The remaining Democratic contenders will hold their final debate Sunday night prior to the "Super Tuesday" contests on March 2. California, New York, Ohio, Connecticut, Georgia, Massachusetts, Minnesota, North Dakota, Rhode Island, Vermont and Washington will all hold either primaries or caucuses on that date.

For more political news, insight into the 2004 presidential election and information on registering to vote, check out ChooseorLose.com.