Brennan Leach, who took the microphone to ask Clinton the first question of the event, wanted the Democratic presidential nominee's thoughts on body image -- and more specifically, what Clinton makes of the things her opponent has said about women's looks.
"At my school, body image is a really big issue for girls my age," said Leach, whose father is State Sen. Daylin Leach, a Clinton supporter. "I see with my own eyes the damage Donald Trump does when he talks about women and how they look."
"I'm so proud of you for asking that question," Clinton responded. "You are right -- my opponent has just taken this concern to a new level of difficulty and meanness."
Clinton, who was on stage with her daughter Chelsea and actress Elizabeth Banks, criticized Trump for his disparaging comments about former Miss Universe Alicia Machado and her weight gain years ago.
"My opponent insulted Miss Universe. I mean, how do you get more acclaimed than that?" Clinton said. "Well, it wasn't good enough. We can't take any of this seriously any more. We need to laugh at it. We need to refute it. We need to ignore it."
The former secretary of state told the 15-year-old that it was "shocking" to see women get called names and judged "solely on the basis of physical attributes," before encouraging her to remember that women are "more than the way you look."
The exchange was the latest example of Trump coming under fire for his remarks about women
and their physique.
The morning after the first general election debate last week, Trump said of Machado: "She gained a massive amount of weight, and it was a real problem. We had a real problem."
The New York businessman has also publicly mocked other women in the past, including comedian Rosie O'Donnell whom he called a "slob" with a "fat ugly face."
Despite the candidate's struggles with women voters, the Trump team -- rather than play damage control using conventional political tools -- has encouraged its supporters to respond by dredging up the extramarital affairs of former President Bill Clinton.
The question of whether Trump is a suitable role model for children also took center stage Monday night at the New Hampshire Senate debate.
The state's Republican Sen. Kelly Ayotte, who is running for reelection against Democratic Gov. Maggie Hasan, was asked by the moderator whether she would point to Trump as a "role model" for kids.
"I think that certainly there are many role models that we have, and I believe he can serve as president and so, absolutely. I would do that," responded Ayotte, who has said she will vote for Trump but has not endorsed him.
Soon after the debate had concluded, Ayotte released a statement taking those remarks back.
"I misspoke tonight," Ayotte said. "While I would hope all of our children would aspire to be president, neither Donald Trump nor Hillary Clinton have set a good example and I wouldn't hold either of them as role models for my kids."