CNN
Donald Trump and Marco Rubio.
Near the debate's opening, the senator immediately criticized Trump for supposedly hiring non-American workers at his hotels.
"If you're going to claim you're the only one that lifted this into the campaign, that you acknowledge, for example, that you're the only one who has been fined for hiring workers illegally," Rubio said.
"No, no I'm the only one on the stage who has ever hired people. You haven't hired anyone," Trump fired back, as the audience applauded.
Several minutes later, the pair went at it again. Rubio returned to his critique, urging viewers to Google Trump's hotel-worker fines.
"If he builds the wall the way he built Trump tower, he'll be using illegal immigrant labor to do it," Rubio said.
Trump retorted: "Such a cute sound-bite."