President Donald Trump waves as he boards Air Force One before departing from Andrews Air Force Base in Maryland on June 18, 2019.

Last week, a veteran Michigan pollster showed Trump trailing Biden by 11 points for that state's 16 electoral votes. Before that, statewide polls in North Carolina and Texas showed Biden ahead by 12 and four percentage points, respectively.

A new Quinnipiac University poll of Florida showed the president trailing former Vice President Joe Biden by nine percentage points, 50%-41%, in their potential matchup for that state's 29 electoral votes. Trump also trailed other possible Democratic nominees, including Bernie Sanders and Elizabeth Warren.

But a look at state-by-state data clarifies the scale of Trump's challenge. As the president tries to rally supporters at a 2020 kickoff rally in Orlando on Tuesday , he is fighting from behind.

Presidents who seek reelection usually win. So Las Vegas oddsmakers, despite President Donald Trump's low-40s approval ratings , still rate him even money for another term. Wall Street expects him to win next year .

Trump carried all those states in 2016, and could do it again in 2020. Polls four years ago showed Trump way behind Hillary Clinton. Sixteen months of campaigning remain.

But the data show that Trump will have to climb out of the deep hole he has dug for himself in nearly two and one-half years in office. Americans know him much better than they did in 2015 – and not in a good way.

Despite a strong economy, this week's NBC News/Wall Street Journal national survey shows that 62% of Americans report themselves uncomfortable or with reservations about a second Trump term; 52% called themselves "very uncomfortable." A Fox News poll showed every major Democratic candidate ahead of Trump – Biden by 10 percentage points.

Of course, results in battleground states determine the Electoral College winner. That's how Trump, while losing the popular vote to Clinton, reached the Oval Office in the first place.

Yet key battlegrounds have grown increasingly unhappy with him. This far from Election Day, with the Democratic nominee still unknown, the best measurement comes from his approval ratings in those places.

The polling firm Morning Consult continually measures state-level presidential approval. Its latest calculations show that Trump's net approval has declined in all 50 of them.

That poses particular problems in the three battleground states where his narrow 2016 victories moved him past the 270 electoral votes needed to win: Michigan (16), Wisconsin (10) and Pennsylvania (20).

In Michigan, the firm shows Trump with approval of 42%, disapproval of 54%. That net-negative of 12 percentage points is 20 points worse than in January 2017.

In Wisconsin, his net-disapproval stands at 13 percentage points – 19 points worse than the start of his term. In Pennsylvania, he's underwater by 7 points, an erosion of 17 points since the start of his presidency.

Indeed, Trump currently faces net-negative job approval rating in 27 states with 328 electoral votes. Add Florida, where he breaks even on job approval but trails in the Quinnipiac Poll, and the eventual Democratic nominee would hold a strong chance of winning 358 electoral votes.

At this point, there's little reason to expect such a lopsided result. No Democrat can count on winning Arizona (where Trump's net-disapproval is 6 percentage points), Ohio (-4 points), North Carolina (-4) or even Iowa (-12).

But winning will require Trump to make up ground across the electoral map at a time when signs point to slowing economic growth and, in personal terms, the public views him negatively.

Some of Trump's predecessors have certainly won from behind. At similar points sixteen months before their reelection contests, Ronald Reagan and Barack Obama each struggled with 43% Gallup approval ratings and disapproval higher than that. Both ended up winning with more than 50% of the vote.

Voters held more favorable personal views of both, however. Reagan's net-disapproval was just two percentage points in mid-June 1983; Obama's was six points in June 2011.

Gallup's most recent survey showed that just 40% of Americans approve of Trump's job performance. A 55% majority disapprove.