During the Massachusetts Senate debate earlier this week, Elizabeth Warren and the other Dem candidates were reminded by the debate moderator that Scott Brown had posed nude in college, and asked what they had done to pay for school. ”I kept my clothes on,” Warren joked, to laughter from the crowd.

Today, Scott Brown was asked by a local Massachusetts radio show to comment on Warren’s joke, and he offered his own joke in response: “Thank God.”

The exchange took place on WZLX this morning, audio of which you can listen to here:

INTERVIEWER: Have you officially responded to Elizabeth Warren’s comment about how she didn’t take her clothes off?

INTERVIEWER: [LAUGHTER] That’s what I said! I said, “Look, can you blame a good-looking guy for wanting to, you know…”

SCOTT BROWN: You know what, listen: Bottom line is, you know, I didn’t go to Harvard. You know, I went to the school of hard knocks. And I did whatever I had to do to pay for school. And for people who know me, and know what I’ve been through, mom and dad married and divorced four times each. You know, some real challenges growing up. You know, whatever. You know, let them throw stones. I did what I had to do. But not for having that opportunity, I never would have been able to pay for school, and never would have gone to school, and I wouldn’t probably be talking to you. So, whatever.

I’m told the Massachusetts papers are writing on this, and Dems are going to jump on it today.

Beyond the back and forth that this exchange is likely to provoke, it highlights what will be a major flashpoint in this campaign: The battle to define Warren as a pointy-headed east coast elitist by pointing to her tenure as Harvard professor. Warren has responded by saying, “I wasn’t born at Harvard,” but Republicans continue to refer to her as “Professor Warren,” which isn’t meant as a compliment.

Brown picked up the charge here by claiming that unlike Warren, he “went to the school of hard knocks.” And now he’s citing his posing nude as proof that he’s had it tougher than Warren did.

It’s going to be particularly interesting to see how Warren handles this one.

UPDATE: Massachusetts Democratic Party executive director Clare Kelly responds:

“Sen. Brown’s comments are the kind of thing you would expect to hear in a frat house, not a race for U.S. Senate. We keep waiting for Scott Brown to take his campaign out of the gutter, but unfortunately it seems like the junior senator has determined that mudslinging and dirty tricks are the only way he can distract Massachusetts voters from his record of voting in lockstep with Tea Party Republicans. Scott Brown’s comments send a terrible message that even accomplished women who are held in the highest esteem can be laughingly dismissed based on their looks.”