DURHAM — The N.C. Senate candidates engaged in a testy debate Thursday, complete with accusations of "gutter" politics and support for "governmental discrimination."

In the last of three televised debates, Republican Sen. Richard Burr and Democratic challenger Elaine Marshall vigorously disagreed on a broad range of issues.

The sharpest exchange came on the question of the military's "don't ask, don't tell" policy for gays.

Marshall said gay people "who want to stand up and defend us, they ought to be able to do that."

But Burr said he thought the current policy, in which gays in the military may not openly proclaim their sexuality, was working, and he didn't think it should change during a time of war. The divide became even deeper when, in response to a question, Marshall said homosexuality was biological while Burr said he didn't know whether it was genetic or a matter of choice.

"This is wrong-headed and discriminatory," Marshall said of Burr's position. "We should not be judging people by the color of their hair, the color of their eyes, or the color of their skin, or other factors they have no control over. That is wrong in America. What you are talking about is governmental discrimination."

Burr shot back: "Secretary Marshall, I'm not sure I referred to somebody's skin color or their hair color. This is a very specific group of individuals. I've made it very clear what my position is. Don't bring race into this."

Burr and Marshall glared at each other after the exchange.

This was the third and final debate between Burr and Marshall.

The one-hour debate was sponsored by the N.C. Association of Broadcasters and was moderated by Judy Woodruff, a senior correspondent with The News Hour on PBS. Libertarian candidate Michael Beitler was excluded, prompting about a dozen placard-carrying supporters to protest outside the UNC-TV studios.

The debate comes just 12 days before the Nov. 2nd election - and in the midst of early voting. The debates were considered particularly critical for Marshall, who has trailed Burr by significant margins according to most polls.

The tenor of the third debate perhaps reflected that - at least according to one recent poll - the Senate race has tightened some.

Burr, content to play defense during the first two debates, went after Marshall Thursday night. He portrayed her as being inconsistent on some issues, citing her statements on possibly raising the retirement age for Social Security.

At one point, Burr compared Marshall unfavorably to his last Democratic opponent, Erskine Bowles, whom he has since befriended. Bowles is now president of the University of North Carolina system.

"I ran a campaign against Erskine Bowles," Burr said. "It was grueling. It was expensive. At the end of the day, Erskine and I never made it personal. We stayed on the issues. We never made up things. The tactic may be to go into the gutter, secretary, but I'm not going there."

When Woodruff asked him to be specific, Burr said he was referring to the accusations made against him in her TV ad.

Marshall fired back that Burr's own ad was judged to have falsehoods by independent fact checking.

The candidates also gave their stances:

On reducing the federal budget deficit: Burr said he would favor rolling back federal spending to 2008 levels. Marshall said she wants to remove the "handcuffs" on the Medicare program that prevents the federal government from negotiating for better prices for prescription drugs. She also favors allowing the Bush tax cuts to expire for those making more than $250,000 per year.

On Afghanistan: Marshall voiced more skepticism about the U.S. effort, saying, "We have got to see an end, we have got to have a finish line." She said if the U.S. was going to spend its money rebuilding a country, it ought to start at home. Burr said he wanted to see whether the current troop surge is successful before deciding whether longer troop involvement is advisable.

On the bank bailout: Marshall criticized Burr for voting for the bank bailout, saying it was unfair to give an advantage to large banks that hand out large bonuses. She also said that Burr's support of earlier legislation deregulating banks helped lead to the Wall Street meltdown. But Burr said he supported only a portion of the bailout, and said Marshall had been inconsistent in her public statements about whether she would have supported it.

rob.christensen@newsobserver.com or 919-829-4532