The declaration came during a campaign event on Thursday and aimed at setting himself apart from his chief GOP rival, former President Donald Trump, who faces two federal prosecutions led by Mr. Smith.

The Florida governor expressed his concern that President Trump, as the Republican nominee, would overshadow the election, focusing on legal issues and investigations rather than addressing the nation's challenges.

Should President Trump become the Republican nominee for the third consecutive time, said Mr. DeSantis, then "the whole election will be about him," his behavior, and "all these different investigations and legal cases."

"Which, look," he added, "I think are unfair. I will fire Jack Smith on day one when I'm president. That is without saying."