General Michael Flynn, an adviser for the Republican presidential nominee Donald Trump, attacked Mark Cuban on Sunday, insisting that the anti-Trump businessman has no business attending Monday night’s debate between Trump and Clinton because he is “not a legitimate person.”

When news first broke that the Shark Tank star will be at the presidential debate, Trump went on the offense and tweeted that he will be inviting Bill Clinton’s former mistress, Gennifer Flowers, to sit at the front row of during the debate.

When NBC’s Chuck Todd asked Flynn about Trump’s invitation to Flowers, he tried divert by saying, “I would just go with what you have seen, and we’ll wait to see what happens tomorrow night.”

“Was it appropriate to invite Mark Cuban?” the Trump adviser continued. “I mean, he’s not a legitimate person. Why is he invited? I mean, again, I would leave this tit for tat. This is about the big issues this country is worried about.”