The Clinton campaign confirmed it did invite Cuban and that his ticket is "one of the best seats we have available" at Hofstra University in Long Island, New York.
“I’m excited to see what happens, but I really don’t know what to expect," Cuban told ABC News today at the red carpet premiere for the ABC show "Shark Tank."
"Obviously, I’m a not a Trump fan. I am a Clinton fan," Cuban said. "I think she’d make a great president. I don’t think he’s got the skill set. Let’s put it this way, if he came on 'Shark Tank,' I wouldn’t make the investment. I just don’t see him as being capable in the least bit.”
He has emerged as a critic of Trump, questioning whether the New York real estate mogul is actually worth $10 billion, as Trump has claimed, and calling on the Republican presidential nominee to release his taxes.
“What he’s done well is put his name on big buildings. ... He’s good at that. Now, whether or not that makes him a billionaire, I don’t know,” Cuban said of Trump in a June interview on 77 WABC’s “Bernie and Sid Radio Show” in New York City. “He’s not transparent enough for us to know that.”
Cuban trolled Trump recently by offering $10 million in exchange for an interview on Trump's policies.
A Rare Moment of Peace
Cuban called Trump "probably the best thing to happen to politics in a long time" in a statement last year on Cyber Dust, a private messaging app Cuban created.
In September of last year, Cuban gave Trump the American Airlines Center in Dallas, where the Mavericks play, free of charge for one of his biggest rallies during the fall cycle.
At that Sept. 14 rally last year, Trump called Cuban "a great guy" and thanked him for allowing him to use the arena.
Back in May, during the veepstakes, Cuban said on ESPN Radio's “Capital Games” podcast that he's "wide open" to being a running mate for either candidate.
But the relationship between Trump and Cuban quickly soured.
Cuban's 180-Degree Turn on Trump
Cuban, in an interview with EXTRA June 21, unloaded on Trump: "It’s rare that you see someone get stupider before your eyes, but he’s really working at it. ...You have to give him credit. It’s a difficult thing to do, but he’s accomplished it."
Cuban went on to explain the reasoning for his 180 on Trump.
“He sent me an email when I started picking on him. … What happened was I really didn’t like Ted Cruz, so I started helping Donald, tried to encourage him, because 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?” he said in that interview.
“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, 58, told CNN while campaigning with Clinton in his hometown of Pittsburgh on July 30, "Donald initially — I really hoped he would be something different, that as a businessperson, I thought there was an opportunity there. But then he went off the reservation and went bat---- crazy."
A History of Rivalry
Cuban and Trump, 70, have been rivals for some time. Before the campaign kicked off, the two would get into frequent Twitter spats. Back in 2012, Cuban dared Trump to shave his head for charity, offering to pay $1 million if Trump went through with it.
Trump subsequently accused Cuban of “trying to use me to get publicity for himself," before, months later, saying, Cuban “has less TV persona than any other person I can think of. He’s an arrogant, crude, dope who met some very stupid people.”
Watch the first presidential debate Monday at 9 p.m. ET. Full live coverage and analysis of the debate will begin on ABCNews.com/Live at 7 p.m. ET.