He told rally attendees to pretend that he's losing so that more people will be motivated to get out and vote for him in the Sunshine State.
"We're way up in Florida," Trump said. "I shouldn't say that, because I want you to go vote. Okay, ready? We're going to pretend we're down. We're down, Pretend, right? We'll pretend we're down."
Hillary Clinton led Trump in five of seven polls of likely voters recently conducted in Florida, while one showed Trump ahead and another found the two candidates tied. A CNN/ORC survey released Wednesday showed Clinton leading by one point among likely voters in a head-to-head matchup.
Trump also repeated his claim at the rally that the FBI was "re-opening" its investigation into Clinton's use of a private email server.
"Did you hear about this little event?" Trump said. "The FBI, reopening the investigation. They're reopening the investigation into Crooked Hillary Clinton."
He congratulated himself for coming up with the moniker, and said: "That's going to be a great term for a president."
Trump's claim echoed the message in a new television ad that the GOP nominee's campaign released Wednesday. In the ad, titled "Corruption," a narrator claims the FBI has launched a new investigation into Clinton, even though the agency has announced neither a re-opening of its previous inquiry into her use of a private server nor an entirely new investigation.
Trump went on to slam Clinton for her use of a private email server as secretary of state, which he said she did "to shield her criminal activity."
If Clinton wins the presidential election, he claimed, it would "create an unprecedented and protracted constitutional crisis."
"The work of government would grind to a halt if she were ever elected," Trump said. "She'll be in court for her entire tenure and she'll be convicted."