"He is becoming ISIS's best recruiter," Clinton said.
"They are going to people, showing videos of Donald Trump insulting Islam and Muslims, in order to recruit more radical jihadists," Clinton added.
Over on CNN after the debate, the question was - are there really videos out there, like the one that Hillary Clinton mentioned, of the Islamic State using Trump as a recruiting tool?
CNN experts weren't so sure.
Clinton wasn't the only one to mention Trump, as Bernie Sanders once more tried to frame this election into a question of economic issues.
"What I say to those people who go to Donald Trump's rallies - understand - he thinks a low minimum wage in America is a good idea, he thinks low wages are a good idea," Sanders said.
Sanders began the debate by apologizing to Clinton over a breach involving Democratic Party voter data, and how some of it got in the hands of the Sanders campaign.
Clinton's response echoed that of Sanders in the first debate, when he gave Clinton a pass on questions about her email troubles while Secretary of State.
"We should move on, because I don't think the American people are interested in this; I think they are more interested in what we have to say about all the big issues facing us," Clinton said to applause.
As for Martin O'Malley, he began the debate by trying to insert himself as often as possible into the questions of the two others on stage, and jabbed repeatedly at both Sanders and Clinton.
At one point, O'Malley said the lack of progress on gun control in Congress was the result of the "flip-flopping political approach in Washington," exemplified by Clinton and Sanders.
They were not pleased.
"Let's calm down a little bit, Martin," Sanders said.
"Let's tell the truth, Martin," Clinton added.
At another point, O'Malley drew boos from the crowd when he took a veiled shot at the ages of his fellow Democrats.
"May I offer a different generation's perspective on this?" O'Malley said.
Social media didn't seem to show any magic moment for O'Malley.
And it did not appear that Sanders had any breakthrough, either.