ORLANDO, Fla. – President Donald Trump returned to the key battleground state of Florida on Tuesday to ask Americans to give him another four years in office, claiming he has kept the promises that helped sweep him into office in 2016.

"I can promise you that I will never ever let you down – I won't," Trump told cheering and chanting supporters who packed a pro basketball arena in downtown Orlando.

While promoting issues like the economy and border security, Trump spent as much time condemning his Democratic opponents as "socialists" and "left-wing" extremists who have tried to destroy him and his family, and have "looked down" on his many supporters.

Signaling a brutal campaign over the next 16-and-a-half months, Trump accused enemies of trying to nullify the results of the 2016 election through investigations of Russian interference and calls for impeachment.

Describing Florida as a "second home," the owner of the Mar-a-Lago resort in Palm Beach reached back for many of the elements that marked his raucous political rallies of 2016.

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Crowds, Jumbotrons, heat:What you should know about Donald Trump's campaign kickoff in Orlando

At length, he criticized then-Democratic nominee Hillary Clinton over her use of private emails, prompting old-time chants of "Lock Her Up." Trump made little reference to the nearly two dozen Democrats who are seeking their party's nomination in 2020, save for a couple of sneering references to "Sleepy" Joe Biden and "Crazy" Bernie Sanders.

These and other Democrats said Trump has succeeded only in dividing Americans, alienating global allies, and slowing the economy with ill-advised tariffs and trade wars that have spooked markets.

Praising Democratic predecessor Barack Obama, Biden tweeted "let’s be clear: President Trump inherited a growing economy from the Obama-Biden administration. And now, he’s in the process of squandering it."

On his Twitter feed, Sanders said "the president won't address our health care crisis or climate change. But he will try to divide us up and go after undocumented people who have very little political power. That is what demagogues always do and that is why he must be defeated."

More:Poll: Biden, Sanders lead Trump in Florida

In an announcement speech that ran longer than an hour, Trump promoted issues like border security and trade tariffs, and excoriated the media and the Democrats for spotlighting the Russian issue and other controversies surrounding his presidency.

"Nobody has done what we have done in two-and-a-half years," he said at one point.

Trump described his election – he lost the popular vote, but won the Electoral College – as "a defining moment in American history," and he urged Americans to give him a second term to finish the job.

During his speech, Trump reviewed many of the events that have marked his first term in office. He condemned the Russia investigation by special counsel Robert Mueller, and accused Democrats and the media of conducting a "witch hunt" designed to "take down our incredible movement."

While Trump claimed "no collusion" and "no obstruction," critics said Mueller provided plenty of evidence of cooperation between Trump's 2016 campaign and the Russians, as well as efforts by the president to obstruct Mueller's investigation.

Trump frequently engaged the crowd, telling them they put him in the White House and they are the ones who are the real targets of political attack. At one point, Trump conducted a "poll" on whether he should keep his 2016 political slogan ("Make America Great Again") or replace it with a new one: "Keep America Great.''

The new slogan won the voice vote by a loud margin.

Frequently meandering off script, Trump also thanked Republican leaders who attended the Orlando rally. He even brought outgoing White House Press Secretary Sarah Sanders to the stage. Speaking less than a week after announcing her resignation, Sanders said that "no one will be a stronger voice" for Trump's re-election.

Though he has never stopped campaigning since he entered the White House more than two years ago, Trump’s rally at a 20,000-seat basketball arena in Orlando marks the formal kickoff of his 2020 re-election bid.

"Our future has never, ever looked brighter or sharper," Trump said.

In preceding the president at the podium, Vice President Mike Pence said the campaign invited supporters to the Orlando basketball arena for one reason: "American needs four more years of President Donald Trump."

Trump did not receive a completely friendly welcome in Central Florida.

The Orlando Sentinel newspaper ran an editorial listing reasons to vote against the incumbent, saying "Donald Trump is in Orlando to announce the kickoff of his re-election campaign. We’re here to announce our endorsement for president in 2020, or, at least, who we’re not endorsing: Donald Trump."

More:Orlando paper posts scathing editorial ahead of Trump's big visit

The campaign event is a far cry from four years ago, when Trump announced his unlikely presidential run by riding down the escalator to the basement food court of the Manhattan skyscraper that bears his name.

This time, Trump will make his case for re-election not as an outsider but as an incumbent who will argue he has delivered on his promises during his turbulent first term but that work still remains to be done on issues like immigration and health care.

“We’re taking on the failed political establishment and restoring government of, by and for the people,” Trump said in a video released Monday by his campaign. “It’s the people, you’re the people, you won the election.”

But Trump formally launches his 2020 campaign surrounded by uncertainty.

Multiple polls show him trailing former Vice President Joe Biden and other Democratic contenders in key battleground states. Trump insists his internal polling shows him ahead, but his campaign severed ties with its pollsters after leaked internal polling showed him trailing Biden by double digits in the key swing states of Wisconsin, Pennsylvania, Florida, and Michigan.

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