Here’s why Donald Trump is so focused on the Florida governor’s race.

President Donald Trump is obsessed with the Florida governor's race. He's making two trips here this week, has been tweeting about it since December and trashed Democratic nominee Andrew Gillum as a "stone cold thief" on Fox News on Monday night.

But there's a good reason why he's so interested: It's critical to his chances for re-election in 2020, according to his former White House political strategist, Steve Bannon.

If a Republican occupies the Governor's Mansion, he could steer donors, party leaders and even the machinery of government in directions that benefit a presidential candidate. (The governor appoints the secretary of state, the state's chief elections officer, for example.)

And Trump would have no more loyal acolyte than former Congressman Ron DeSantis, who used Trump's endorsement — and only Trump's endorsement — to win the Republican gubernatorial primary this year.

Bannon told the Times on Friday that the effect of next week's election on the 2020 race will be "big time."

"If Rick Scott was not governor, it would have been very hard for us to win Florida" in 2016, Bannon said.

With just a week left, Trump is stumping for DeSantis and Gov. Rick Scott tonight in Fort Myers and Saturday night in Pensacola.

And the rhetoric from the president and his supporters has also ramped up.

He called Gillum a "stone cold thief" during an interview with Fox News host Laura Ingraham on Monday night.

"Here's a guy that, in my opinion, is a stone cold thief, and his city, Tallahassee, is known as the most corrupt in Florida, and one of the most corrupt in the nation," Trump said.

Trump justified calling him a "thief," which he first did on Twitter on Monday, by bringing up the Hamilton ticket that was given to Gillum by an undercover FBI agent.

"The FBI offered him tickets at $1,800 a piece and he took 'em," Trump said. "He took a trip with the same FBI agent. I guess he was posing as a developer or something. The man stone cold took this stuff. I don't even think he should be allowed to continue on with the race."

Trump also wondered how Gillum could be polling so well, saying that Gillum would turn Florida into Venezuela and that Gillum's Trump-endosrsed opponent, Republican Ron Desantis, is a "very good person."

"He's a disaster, and how he's even close to being tied is hard to believe," Trump said of Gillum.

Gillum responded Tuesday by saying "the president should grow up."

"We're adults. And I think that this moment requires adult conversations," Gillum said. "A thief? If we're stealing anything, it's hearts and minds, and we're going to win this election because of that.

"I get that this is difficult for them to accept, the second home of the president is going to go the way of the Democrats."

During a Monday press briefing, White House Press Secretary Sarah Huckabee Sanders defended Trump's "thief" tweet by saying Gillum "is under FBI investigation."

It's not publicly known whether Gillum is under an "active" FBI investigation. Gillum has said agents have assured him he's neither a target nor a focus of the Bureau's long-running probe into corruption in Tallahassee. The FBI has declined to comment on their case, which has yet to bring charges against anyone.

The accusations against Gillum have revolved around his coziness with former lobbyist and friend Adam Corey, who arranged or went on seven trips with Gillum in 2016, including one to New York with undercover FBI agents. Gillum is facing an ethics complaint that he failed to report gifts from Corey and undercover FBI agents worth more than $100, but it's unlikely those would rise to the level of a federal crime.

Nevertheless, former New York City Mayor Rudy Giuliani took to Twitter at 2:22 a.m. Tuesday to assert, with no factual basis, that Gillum "is reportedly under criminal investigation by the FBI."

Despite Trump's incalculable assistance, Bannon told the Times that "DeSantis is in the fight of his life."

"It's going to come down to the wire on the last day," Bannon said. "Gillum's proven that he's a very tough competitor. … They may have miscalculated at first how tough Gillum was going to be."

Times Correspondent William March and Staff Writer Kirby Wilson contributed to this report.