CNN's Jake Tapper and TV One's Roland Martin moderated, as the candidates made their case ahead of Tuesday primaries in Florida, Ohio, Illinois, North Carolina and Missouri.
Here are a few of the most memorable lines. (For the blow-by-blow, check out the CNN live blog
On Trump's responsibility for recent violence at his rallies: "What Trump has done is like a case of political arson."
On when she supported the death penalty: "...in cases where there has been horrific mass killings, that's really the exception that I still am struggling with and that would only be in the federal system."
On what she's hearing from people around the world about Trump: "I'm having foreign leaders ask if they can endorse me to stop Donald Trump."
On when to use force in global conflict: "I don't think it's an either-or kind of question. I believe we have to use every tool at our disposal, our diplomacy, our development and our strong cultural influence around the world as well as our defense."
On fracking: "I'm going to do everything I can to try to regulate it and limit it. No president can stand up before you and say they're going to ban it. ... I don't want to make a promise I can't keep."
On clean energy -- a line we might hear again in the fall: "We are going to put a lot of coal miners and coal companies out of business."
: "I hate to say this, because I hate to disparage public officials, but Donald Trump is a pathological liar
On Trump's suggestion he would pay the legal fees for a man who sucker-punched a protester at a rally: "Donald Trump is literally inciting violence with his supporters. He's saying, 'If you go out and beat somebody up, that's OK, I'll pay the legal fees.' That's an outrage and I hope Mr. Trump tones it down big time."
On concerns voiced by, among others, Marco Rubio that someone could be killed at a Trump rally: "Sen. Rubio has a legitimate concern."
On how he would handle the use of lethal force by police: "My Department of Justice will investigate every killing of an American held in police custody or killed while being apprehended -- an automatic Department of Justice investigation."
On one way he would pay for tuition-free college at public institutions: "I believe we should impose a tax on Wall Street speculation. If we could bail out Wall Street, now it's Wall Street's time to help the middle class of this country."
On a lack of investment in low income communities: "What is going on in areas in Columbus, in areas all over this country, is a national disgrace."
On free trade and Trump: "Nobody is talking about building a wall around the United States. Of course we value trade -- Oh, I beg your pardon, there is one guy who is talking about building a wall. Let me rephrase it, no rational person is talking about building a wall."
Revealing his best cross-aisle friend, Oklahoma Sen. James Inhofe: "Jim is a climate change denier and he is really, really conservative. But you know what, he is a decent guy and I like him, and he and I are friends."