U.S. President Donald Trump arrives for a rally at the Aaron Bessant Amphitheater on May 8, 2019 in Panama City Beach, Florida.

Four years after he took an escalator ride that upended American politics, President Donald Trump will officially launch his 2020 reelection bid Tuesday.

Even after he took office in January 2017, the president never stopped campaigning. He has held rallies in key electoral states and reeled off his achievements at every turn. But the event in Orlando, Florida, on Tuesday will kick off a 17-month slog in which Trump will try to knock off a Democratic challenger intent on denying him a second term.

Trump starts the campaign season in an unusual spot for a president: overseeing a strong economy but facing low approval ratings. He now sets out to convince voters in states where he scraped out 2016 victories — from Florida to Pennsylvania and Wisconsin — that he deserves another four years in the White House.

Early warning signs are flashing. In recent days, Trump has fixated on polls — both public and conducted by his campaign — that show him trailing several Democratic presidential candidates.

After a national Fox News poll released Sunday found the president trailing former Vice President Joe Biden and Sen. Bernie Sanders by 10 and 9 percentage points, respectively, the president tweeted that the network's surveys "are always bad for me." He claimed "our polls show us leading in all 17 Swing States" — without referencing any specific numbers.

Trump tweet: .@FoxNews Polls are always bad for me. They were against Crooked Hillary also. Something weird going on at Fox. Our polls show us leading in all 17 Swing States. For the record, I didn't spend 30 hours with @abcnews, but rather a tiny fraction of that. More Fake News @BretBaier

A leaked internal poll taken by the Trump campaign in March showed the president trailing Biden by double digits in Wisconsin, Pennsylvania, Florida and Michigan, all of which he won in 2016. It also found him lagging the former vice president in North Carolina, Iowa and Georgia, states he won by comfortable margins in his first presidential bid.

Biden leads Trump by 9 percentage points in Florida, while Sanders and Sen. Elizabeth Warren sit 6 and 4 percentage points ahead of the president there, respectively, according to a Quinnipiac University poll released Tuesday. All of those leads are larger than the survey's margin of error.

By kicking off his campaign in Orlando, Trump hopes to keep his foothold in a state that delivered 29 electoral votes on his way to the White House in 2016. The president carried Florida by about a percentage point in 2016. Last year, Republicans won closely contested statewide races for governor and the U.S. Senate there.