Addressing a crowd of thousands at Orlando's Amway Center, Trump complained he had been "under assault from the very first day" of his presidency by a "fake news media" and "illegal witch hunt" that had tried to keep him and his supporters down.
And he painted a disturbing picture of what life would look like if he loses in 2020, accusing his critics of "un-American conduct" and telling the crowd that Democrats "want to destroy you and they want to destroy our country as we know it."
"A vote for any Democrat in 2020 is a vote for the rise of radical socialism and the destruction of the American dream," he said, ripping "radical" and "unhinged" Democrats even as he made only passing mention of any of the men and women running to replace him.
The apocalyptic language and finger-pointing made clear that Trump's 2020 campaign will probably look a whole lot like his improbably successful run three years ago. While Trump's campaign has tried to professionalize, with shiny office space and a large and growing staff, and despite two-and-a-half years occupying the Oval Office as America's commander-in-chief, Trump nonetheless remained focused on energizing his base and offering himself as a political outsider running against Washington.
And he appeared eager for a rerun of 2016, spending considerably more time focused on former Democratic rival Hillary Clinton, whose name elicited "Lock her up!" chants, than on his current 2020 challengers, even though she is not on the ballot.
A boisterous crowd of thousands of Trump supporters, many in red hats, began gathering outside the arena on Monday and spent Tuesday braving downpours and listening to a cover band as part of a "45 Fest" the campaign organized to energize the crowd.
"Trump has been the best president we've ever had," said Ron Freitas, a retired Merchant Marine and registered Democrat from Orlando.
Close by, hundreds of anti-Trump protesters clapped and took photos when a 20-foot (6-meter) blimp of a snarling Trump baby in a diaper was inflated. Some members of the far-right hate group Proud Boys were also spotted marching in Orlando outside the rally.
Trump aides scheduled the kickoff near the four-year anniversary of the day when the bombastic reality television star and New York tabloid fixture launched his longshot campaign for president with a famous escalator ride in front of a crowd that included paid actors.
Trump spoke fondly of his 2016 run, calling it "a defining moment in American history." And he said that, in the years since, he had fundamentally upended Washington, staring down "a corrupt and broken political establishment" and restoring a government "of, for and by the people."
Of course, Trump never really stopped running. He officially filed for re-election on January 20, 2017, the day of his inauguration, and held his first 2020 rally in February, 2017, in nearby Melbourne, Florida. He has continued holding his signature "Make America Great Again" rallies in the months since.
Still, he gave lip service to the hype, telling the Orlando crowd he was standing "before you to officially launch my campaign for a second time."
He asked the crowd whether he should stick with "Make America Great Again" or upgrade. His new campaign slogan - "Keep America Great" - was greeted with boisterous cheers.
Trump is hoping to replicate the dynamics that allowed him to capture the Republican Party and then the presidency in 2016 as an insurgent intent on disrupting the status quo. Back then, he successfully appealed to disaffected voters who felt left behind by economic dislocation and demographic shifts. And he has no intention of abandoning that mantle, even if he is the face of the institutions he looks to disrupt.
He underscored that on the eve of the rally in the must-win swing state of Florida, returning to the hard-line immigration themes of his first campaign by tweeting that, next week, Immigration and Customs Enforcement "will begin the process of removing the millions of illegal aliens who have illicitly found their way into the United States." That promise, which came with no details and sparked Democratic condemnation, seemed to offer a peek into a campaign that will largely be fought along the same lines as his first bid, with very few new policy proposals for a second term.
Early Democratic front-runner Joe Biden said Tuesday that Trump's politics are "all about dividing us" in ways that are "dangerous - truly, truly dangerous."
Another leading Democratic contender, Vermont Sen. Bernie Sanders, said Trump had delivered "an hour-and-a-half speech of lies, distortions and total, absolute nonsense."
But those involved in the president's reelection effort believe that his brash version of populism, combined with his mantra to "Drain the Swamp," still resonates, despite his administration's cozy ties with lobbyists and corporations and the Trump family's apparent efforts to profit off the presidency.
Advisers believe that, in an age of extreme polarization, many Trump backers view their support for the president as part of their identity, one not easily shaken. They point to his seemingly unmovable support with his base supporters as evidence that, despite more than two years in office, he is still viewed the same way he was as a candidate: the bomb-throwing political rebel.
Trump tried to make the case that he had made good on his 2016 promises, including cracking down on illegal immigration and boosting jobs.
Near the end of the rally, Trump ran through a list of promises for a second term, pledging a new immigration system, new trade deals, a health care overhaul and a cure for cancer and "many diseases," including the eradication of AIDS in America.
Florida is considered a near-must-win state for Trump to hold onto the White House, and both parties have been mobilizing for a fierce and expensive battle in a state that Trump has visited as president more often than any other.
While Trump bested Clinton there in 2016, a Quinnipiac University poll released Tuesday found Biden leading Trump 50%-41%, and Sanders besting him 48%-42%.
Lemire reported from New York. Associated Press writers Kevin Freking, Josh Replogle, Zeke Miller and Juana Summers contributed to this report.
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