Donald Trump hits 'dopey' Mark Cuban, threatens to bring Gennifer Flowers to debate

Trump slams Cuban, threatens to bring Gennifer Flowers to debate

Ahead of what could be a pivotal first debate, Republican presidential nominee Donald Trump blasted billionaire Mark Cuban, a prominent backer of Democratic nominee Hillary Clinton, as "dopey," threatening to bring Bill Clinton's former mistress to the event.

The two wealthy moguls sparred on Twitter—a favorite hobby of both Trump and Cuban—after the GOP nominee blasted the owner of the Dallas Mavericks for agreeing to a prominent slot in the audience of the first presidential debate.

Clinton and Trump will stage their first face-to-face confrontation at Hofstra University in Hempstead, New York. On Saturday, Trump threatened to bring Gennifer Flowers —the former paramour of ex-president Bill Clinton—as a guest if Cuban sat in front.

Trump tweet

Cuban has emerged as one of Clinton's most prominent backers, and a relentless critic of the New York real estate mogul. The billionaire has questioned everything from Trump's net worth, to his business savvy and his fitness to serve as Commander in Chief.

Yet it wasn't always thus. In response to Trump's tweet, Cuban posted that the two once were close enough to have a phone conversation, one in which Trump apparently referred to them as "twins."

Cuban Tweet

Yet the plot thickened when a Twitter account appearing to belong to Flowers backed Trump, and said she would appear at the debate. That account was not verified, however.

Earlier this month, Cuban said he would cut a check to Trump's charity of choice if he would let Cuban interview him on his policies.

The "Shark Tank" star promised that the interview would be conducted by Cuban along with a broadcast crew.

Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank," which features Mark Cuban as a judge.