Trump's campaign manager, Kellyanne Conway, echoed Pence's comments, saying Flowers isn't expected to be at the presidential debate as Trump's guest.

"Mr. Trump was putting them on notice that we could certainly invite guests that make it into the head of Hillary Clinton," Conway said Sunday morning.

Debate commission co-chairman Frank Fahrenkopf warned both nominees against using their invites to try to disrupt the debate.

"We're going to frown upon — I will tell you this right now — whether or not a Republican or Democrat or anyone else attempts by use of the tickets in placing people in a front-row or not to try to impact the debate," he said Saturday on CNN.

"It's wrong. We would frown upon Mr. Cuban being in the front row if his purpose is to somehow disrupt the debate. Likewise, if Mr. Trump was going to put someone in the front row to try to impact things."

Still, Fahrenkopf said the debate commission has been working with the both campaigns' staff and doesn't expect any problems.

"They're approaching this in a very dignified manner — the way I think it should be approached," he said.

On Sunday, members of Clinton's campaign defended the decision to invite Cuban to the debate, touting his accomplishments and denying it's an attempt to annoy Trump.

Clinton's chief strategist, Joel Benenson, called Cuban a "successful businessman" whose economic beliefs often match Clinton's. "I think it's legitimate to have a businessperson sitting there who's been advocating for you because of your economic policies," Benenson said on "Fox News Sunday." "I think it's legitimate to have a businessperson sitting there who's been advocating for you because of your economic policies," Benenson said on "Fox News Sunday."

Benenson noted that Cuban believes in things such as profit-sharing to help increase wages. He pointed to the many businesspeople who have endorsed the Democratic nominee and touted her plans to grow the economy and help get incomes rising for working Americans.

"As opposed to a candidate like Donald Trump, who says he thinks wages are too high in America and we should get rid of the federal minimum wage," Benenson added.