Mark Cuban destroys Donald Trump: 'It’s rare that you see someone get stupider before your eyes'

Billionaire businessman Mark Cuban was once friends with GOP candidate Donald Trump. But that relationship seems to have gone south in the course of Trump's bid for president.

Recently, Dallas Mavericks owner and "Shark Tank" star Cuban was asked by Extra to weigh in on Trump -- and his response was not flattering.

“You know what? It’s rare that you see someone get stupider before your eyes, but he’s really working at it,'" Cuban said. "You have to give him credit. It’s a difficult thing to do, but he’s accomplished it.”

Cuban also revealed he hasn't talked to Trump in weeks.

“He sent me an email when I started picking on him," Cuban said. "What happened was I really didn’t like Ted Cruz, so I started helping Donald, tried to encourage him, 'cause I thought he’d be, and to this day thought he’d be a better candidate than Ted Cruz… But at some point, you’ve got to start learning and understanding the issues, you know? Donald has been at this a year but you don’t look at him and say, ‘Wow, he’s gotten so much smarter on this topic or that topic.' In fact, you look at him and say, ‘What the hell are you talking about?' That’s not good for America.”

Cuban challenged Extra host Renee Bargh to name one good deal Trump has done.

"I can't," she said.

"Neither can he," Cuban shot back, adding, “He’d get kicked out of 'Shark Tank' so fast, it would make your head spin.”

Watch the interview, as posted by Extra, here: