The comments came at the end of the debate, when Gregory asked Buck to expand on some recent comments he'd made about "lifestyle choices" when expressing his support for the military's "Don't Ask, Don't Tell" policy. Buck said he believed being gay is a choice, and Gregory asked him: "based on what?"
"Based on what?" Buck said. "I guess you could choose who your partner is."
"I think that birth has an influence over it, like alcoholism and some other things," Buck continued. "But I think that, basically, you have a choice."
The debate began with a discussion of the Tea Party, which is credited with helping Buck defeat the Republican party favorite, Jane Norton, in the primary. Buck rejected arguments that the Tea Party was made up of people outside the political mainstream.
"I think its a legitimate political movement," Buck said. "Folks are not going to try to send the same type of Republican to Washington D.C."
For his part, Bennet said some of his favorite campaign events have come when Democrats, Republicans, Independent and Tea Partiers have been in the same room together.
"When folks are together in a room, they actually have to listen to each other," he said.
Buck was forced to address charges that he has flip-flopped on a number of issues since winning the primary. He blamed Democratic trackers for the controversies, including one video that showed him at a campaign event expressing support for getting rid of the 17th Amendment, which allows for the direct election of senators.
"It is easy when you have a tracker and they have a hundred examples of answers, and the questions are coming at you from different angles, to use tape that shows a slight deviation in the answer," Buck said. "It is not fair to say that I have backtracked on those issues."
"This is a different year than most years," Buck went on. "We have got to tell the American people that we have to live with less. We have a $13.5 trillion debt. And the only way to do that is an honest campaign, with honest people. And I have let people know my heart. It hasn't always been the same exact words to the same questions... but they know where I'm coming from."
But Bennet charged that Buck has indeed backpedaled on a number of issues since the primary, including social security, the department of education, and the so-called "personhood" amendment in Colorado.
"I think it is enormously important," Bennet said. "We're never going to say exactly the same thing every second of every day. But the flip-flops in this race is are unbelievable."
Buck responded by hitting Bennet for "false, misleading, deceitful" ads.
On spending, Bennet defended his votes on the stimulus and health care reform. But he argued that his votes weren't endorsements of the way Washington works.
"The choices are tough. And the politics right now are not supporting the aspirations that we have for our kids and our grandkids," Bennet said.
"Senator Bennet does one thing in Washington D.C. and then comes back to Colorado and says a completely different thing," Buck responded. He criticized Bennet for participating in the accumulation of $3 trillion in debt, and said that Bennet had to "take responsibility" for it.
"I have said over and over that Republicans are every bit as much to blame as Democrats," Buck said, when asked about debt accumulated under the Bush Administration. "And I am not going to be one of those Republicans when I get to Washington."
"Just to be clear on that point," Bennet interjected. "The budget proposals that he's made would blow -- without even talking about the tax cut extensions -- $1.3 trillion more of a hole into our budget than we already have."
The subject of a rape case that Buck declined to prosecute as Weld County DA in 2005 came up. The case has been in the media in the last week, as the victim has stepped forward once more to criticize the way that Buck handled the case and his conversations with her.
"I don't regret the way I talk to her. I think it is important that a prosecutor approach a victim with a certain amount of reality," Buck said. "I didn't blame her, at all."
Asked to explain comment he made to a Colorado paper at the time that a jury could believe the case was an instance of "buyer's remorse," he said the phrase was one of 5 or 6 reasons he gave for why a jury might decline the case.
"One of the reasons was the fact that she had regretted this relationship, that she had buyer's remorse as a result of the relationship that she had with this young man," Buck said.
Bennet responded that Buck's words were the "wrong way" to talk.
"Look I have a lot of sympathy of the victim in this case," Bennet said. "He just used the language again. 'Buyer's remorse.' And as a the father of three little girls, I just think that's the wrong way to talk about this kind of set of circumstances. Especially when you're a prosecutor."
The TPM Poll Average for this race shows Buck leading Bennet 47.9%-44.1%.
[Ed note: this piece was edited after publication.]