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WASHINGTON — President Donald Trump railed against Democratic gubernatorial candidate Andrew Gillum and Sen. Bill Nelson at a Florida campaign rally Wednesday night in the president's final dash to keep GOP control of Congress in the midterm elections.

But Trump, who has repeatedly gone after the Democratic hopeful this week, left most of the attacks up to Gillum's Republican challenger, former Rep. Ron DeSantis, who joined the president on stage in Ft. Myers.

"I'm the only guy that can credibly say that I am not under investigation for corruption by the FBI” DeSantis said, referencing comments made by Trump earlier in the week when he called Gillum a "stone-cold thief" and implied without evidence that Gillum was under investigation in a corruption probe in Tallahassee, where he serves as mayor.

"Maybe we should impeach Gillum," DeSantis said to the Florida crowd, which prompted supporters to chant "Lock him up!" — something which is usually reserved for Hillary Clinton at Trump campaign events.

The closely fought governor's race turned ugly weeks ago when a white supremacist group targeted voters with a telephone robocall imitating Gillum in a minstrel voice. In October, another call circulated calling Gillum a "negro" and a "monkey."

"Race is at the center of the gubernatorial election, there is no question about it," said Daniel Smith, a political science professor at the University of Florida. "The race card is overt...We aren't talking dog whistle racism, this is attack dog mode."

Trump got in a few of his own shots at Gillum, who polls show is in a toss up race against DeSantis.

"In Tallahassee, they've had the highest crime rate," Trump said, implying that under Gillum crime rose. "He cannot keep Florida safe." Although Leon County, where Tallahassee is located, tops the crime rate in the state, the county's crime rate has decreased during Gillum's tenure as mayor.

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The president also attacked Nelson, who is facing a challenge from term-limited Republican Gov. Rick Scott in another contest that is too close to call.

"I am here a lot and I never see Senator Nelson until six months before the election," Trump said.

Trump also double downed on his immigration message in Florida.

"We are getting prepared for the caravan, folks, you don't have to worry about that," Trump said in reference to migrants traveling through Central America and Mexico, hoping to reach the U.S. border. "They've got a lot of rough people in those caravans, they are not angels.”

Trump reiterated his controversial commitment to end birthright citizenship.

"We will end it," he said, promising to "keep them out of the country."

Birthright citizenship is established the 14th Amendment and abolishing it would require Trump to overcome major legal and legislative hurdles.

Before taking the rally stage on Wednesday, Trump said that he always strives to to tell the truth — "when I can" — in an exclusive interview with ABC's Jonathan Karl.

"Well, I try. I do try ... and I always want to tell the truth. When I can, I tell the truth. And sometimes it turns out to be where something happens that's different or there's a change, but I always like to be truthful," Trump said.

Trump also restated his belief that the migrant caravan is an "invasion" on the U.S.

"When you look at some of them, when you look at some of the people in them, yeah, I think it can be considered an invasion. We can't have it."

Trump won Florida in 2016 by a little over 1 percentage point and the state will play a critical role in his re-election.

Like many of Trump's midterm rallies, the rally served the dual purpose of revving up the base before midterms while also laying the groundwork for his 2020 campaign. And it won't be his last stop in Florida before Tuesday's election — Trump will return on Saturday for a rally in Pensacola.

"He is going to the most Republican places in the state short of Panama City, which was just destroyed by a hurricane,” said Rick Wilson, a GOP strategist from Florida and an outspoken critic of Trump. "Fort Myers is three things: Very Republican, very conservative and very, very old. That is his friendly audience which should tell you that it is all about 2020. It is a base-only election for Trump."

Trump's Wednesday night event was the first of 11 campaign events he plans to hold around the country in the last six days before midterm elections.