Hillary Clinton will be the next president of the United States if Donald Trump wins the Republican presidential nomination, according to Jeb Bush.

Appearing on WBZ-TV, the CBS affiliate in Boston, the former Florida governor continued his oft-used assertion that Trump is "not motivated to win the presidency," not a "serious candidate" and suggested that Trump is campaigning in service of Clinton, the Democratic front-runner.

“I don’t know how else to describe it,” Bush told host Jon Keller, according to CBS. “He’s motivated for some reason, but he’s not motivated to win the presidency.”

“He would make it impossible for a Republican to win if he continues down this path,” Bush said, reported The Blaze. “Look, he’s not a serious person, he’s not a serious candidate. We’re living in serious times and his proposals are completely unserious.”

Until recently, Clinton, too, thought Trump was not meant to be taken seriously, but she changed her view this week as Trump proposed temporarily banning Muslims from entering the U.S.

Appearing on NBC’s Late Night with Seth Meyers on Thursday, Clinton said, “You know, I have to say, Seth, I no longer think he’s funny,” The Daily Beast reported. She added: “I think for weeks, you know, you and everybody else were just bringing folks to hysterical laughter and all of that. Now he has gone way over the line, and what he’s saying now is not only shameful and wrong, it’s dangerous.”

In Bush's interview, he suggested that perhaps the true motivations for Trump's candidacy was to simultaneously sink the Republican party and support Clinton.

"People have kind of forgotten that he was a Democrat not so long ago, that he supported Hillary Clinton," Bush said, adding, "That he thought Hillary Clinton would be a good negotiator with Iran. That turned out to be great, wasn't it?"

“Whether it’s motivated by him or not, his winning the Republican nomination would guarantee that Hillary Clinton would be elected president,” said Bush.