Republican presidential nominee Donald Trump said his Democratic rival Hillary Clinton "has to go to jail" over her email server issue -- comments that mark a major departure from the American political tradition.

Trump on Wednesday, firing up a large crowd of loyal supporters during a swing through Florida, also laid into the Democratic nominee over her health and seized on disclosures from hacked emails of her campaign chairman, John Podesta, released by Wikileaks, CNN reported.

The broadsides came as Trump sought to get the focus back on his presidential rival, following a slump in his poll numbers triggered by his latest debate performance along with lewd and sexually aggressive remarks on a 2005 video that surfaced last week.

At a morning rally in Ocala, Trump said that he was "embarrassed" Congress had not done more to probe Clinton after the FBI decided not to seek charges against her over the private email server she used as secretary of state.

"Do they make deals like this?" Trump asked.

"This is the most heinous, the most serious thing that I've ever seen involving justice in the US -- in the history of the US."

"We have a person that has committed crimes that is now running for the presidency."

Later on, after moving on to Lakeland, Florida, Trump again renewed his vow to appoint a special prosecutor to investigate Clinton if he is elected.

Clinton "has to go to jail," Trump warned, adding that the lawyers working for her over the email issue should also be incarcerated.