Cuban endorsed Clinton in July, and a Clinton campaign aide told ABC News that he will have "one of the best seats we have available.”
Clinton campaign manager Robby Mook was asked in his appearance on "This Week" about the possibility of Flowers attending the debate.
Mook said the debate "is supposed to be about how the candidates are going to make a difference" in Americans' lives. "It’s a time for them to reveal their plans,” Mook told ABC News’ George Stephanopoulos. “If this is what Donald Trump wants this debate to be about, that’s up to him.”
Mook added on Trump, "He's a reality TV star. He’s very experienced at providing television entertainment. The presidency is not about entertainment. It’s about serious decisions.”
ABC's Veronica Stracqualursi and Liz Kreutz contributed reporting.