Washington (CNN) President Donald Trump is flinging scalding rhetoric on immigration and staging a raucous rally with his true believers in a bid to recreate his magic 2016 formula on the day he formally launches his quest for a second term.

On Tuesday evening, Trump will appear before a besotted Florida crowd, seeking to once again electrify his base with politically incorrect bombast as he embarks on an apparently narrow but credible path back to the White House.

Yet while he never tires of reliving his first White House race and the sweet triumph of election night, Trump must face a truth even he will struggle to deny once the euphoria of his return to the trail abates: 2020 may not be like 2016

Trump must prove he can recast the political spell that defied pundits and probability and delivered one of the most shocking election wins in history, at a different political moment.

This time, he won't just be able to run against the other side and a rotten political establishment . He must defend the most controversial presidential record in decades against a Democratic Party that may be in ideological turmoil but is unified on one goal: ejecting him from the Oval Office.

Cresting crises overseas, endless scandals, personal feuds, the President's flattery of tyrants, impeachment talk and an impossible-to-ignore presidency that's barged into every American's life in a draining two and a half years will complicate Trump's narrative this time.

Democratic nominee Hillary Clinton repeatedly said Trump was temperamentally, intellectually and personally unfit for the presidency -- now Democrats believe they have the evidence to prove it.

But the President, who repeatedly claimed and proved in 2016 that he was his own best strategist, is keeping faith in the old playbook.

"I'm just telling you I'm going to do it the same way I did it the first time," Trump told ABC News in a recent interview

That already means fresh and polarizing anti-immigration campaigns, a return to the cultural warfare that stoked anger among his supporters in 2016 and more attempts to devalue the truths voters depend on to make an informed electoral choice.

"Next week ICE will begin the process of removing the millions of illegal aliens who have illicitly found their way into the United States. They will be removed as fast as they come in," Trump tweeted on Monday night, without providing specifics.

Trump on Monday seized on local media reports in Florida, saying "thousands" of supporters were already lining up for the rally the following evening in Orlando.

"Large Screens and food trucks will be there for those that can't get into the 25,000 capacity arena," Trump tweeted . "It will be a very exciting evening! Make America Great Again!"

Troubling omens

The President will crank up the pace of a campaign he never really shuttered after he won the White House, facing troubling omens that suggest he may struggle to re-create the magic.

His approval ratings are mired in the low 40s -- dangerous territory for a President seeking reelection, and he's presiding over a nation exhausted by investigations, outrageous presidential behavior, and the cultural and social discord he fomented as an instrument of his own power.

There are signs Trump may be in denial about the magnitude of his task, after he fired pollsters who brought him bad news, which was leaked, and he told supporters not to believe anyone who says he's not winning.

Democrats are trying to destroy the Trump coalition at its foundations by challenging his claim to be a champion of "the forgotten men and women" he lionized in his stark inaugural address. In a six-figure digital ad buy anticipating his Florida rally, Democratic super PAC Priorities USA blasted Trump for gutting Obamacare and enriching the wealthy with his tax cut.

"All Trump cares about are the people at the top," says one ad.

Yet no one is writing Trump off, partly because of the strong economy and historically low unemployment that is political gold for an incumbent. He has delivered for many conservatives, seating two new Supreme Court justices and scores of lower court judges in alliance with GOP Senate Majority Leader Mitch McConnell, and will expect them to honor their bargain at the ballot box.

The 2020 race will test whether Trump really is an aberration. He will seek to prove that his unconventional character, shameless approach and magnetism to supporters mean that historical trends and the raw data of polls can be tossed out of the window for a second time.

Certainly, analysts who all but consigned him to defeat in 2016 will be more wary of their polling numbers this time because of the way Trump shattered political logic last time around.

'American greatness'

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In an eve-of-launch email, the President tried to revive the underdog spirit that drove a larger-than-expected 2016 turnout.

"When I launched my 2016 Presidential campaign 4 years ago today, the FAKE NEWS media told us that we had NO CHANCE of winning, but I believed in our tremendous potential because of YOU," Trump, still the anti-establishment outsider, wrote.

"You showed them what American Greatness looks like, and we're just getting started," he said.

Trump won the presidency by smashing taboos and tapping into angry anti-elite sentiments most real politicians didn't even hear. He gave voice to Americans left behind in an unequal economy and bent reality to sketch his own version of truth.

His freewheeling, unchained stream-of-consciousness campaign was a revelation. And he stirred resentment and personal liberation among his supporters that drove them into polling places in November 2020.

Within his fired-up crowds, there was an almost anarchic sense of fun that often instead came across in the TV footage as that of a demagogic candidate berating his enemies. One of the key early tests of his campaign will be whether the President can still summon that priceless connection.

Trump destroyed his Republican opponents and Democratic nominee Hillary Clinton by doing anything it took to win. He's signaling he will do the same again, after suggesting last week that he might look at any dirt on an opponent offered by a foreign power before telling the FBI.

He will have a much more professional, targeted personal campaign machinery to help him after relying mostly on the Republican National Committee in 2016 -- and has already raised nearly $100 million to power his bid for a second term.

The President believes that he will be able to dictate the shape of the campaign much as he did in 2016 -- with streams of tweets that knock his foes off balance.

"I put one out this morning. And as soon as I pressed the button, they said, 'We have breaking news.' Every network, every station. 'We have breaking news.' They read my tweet," Trump told ABC News.

Trump, however, will almost certainly not benefit from the same unfiltered coverage he enjoyed in his 2016 primary campaign from media outlets, which have become wiser to his tricks.

Trump's narrow path

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But it is already clear while he has a credible path back to the White House, Trump has no room for error.

It was one thing to prevail as an outsider with no expectations, who even his campaign didn't expect to win. It's another to make history a second time, with everything to lose and the ignominy of being a one-term President beckoning.

Some 17 months before Election Day, it's already clear Trump has only one way to win -- by reassembling his Midwest blue-collar coalition to add to his dominance in the South, while grabbing a likely narrow victory in Florida, which has 29 electoral votes and where he stunned Clinton in 2016.

He has never made any effort to broaden his support, as most presidents do when eyeing second terms in the knowledge they may struggle to relight the fire of their first runs.

The President kept his base close and energized with a staggering 59 rallies since early 2017, according to a CNN count, letting off steam and offering programing for the conservative media machine.

The strategy was a success in that Trump regularly polls in the high 80s among Republican voters, and has remade the party around his populist, nationalist image.

But almost all of his rallies were in solid Trump country, reflecting the base-or-nothing strategy that depends on the same huge GOP enthusiasm as 2016 and a depressed Democratic turnout that seems less likely given the angst among liberals over the President.

Early polling numbers are not predictive, but Trump is going out of his way to dismiss leaked internal polls that appear to show him in trouble in key swing states and that raise questions about his limited voter net.

Most national matchup polls also show Trump losing to most Democratic candidates -- with Joe Biden especially strong -- one reason why sources have told CNN that Trump has been peppering his staff with concerns about the former vice president.

The Democratic front-runner on Monday looked to poke the President's insecurities a little bit more ahead of his big Florida announcement.

"I plan on campaigning in the South. I plan and if I'm your nominee, I plan on winning Georgia, North Carolina, South Carolina, believe it or not," Biden said. "And I believe we can win Texas and Florida, if we look at the polling data now."