Donald J. Trump and Ron DeSantis remade Florida into the red-hot center of the Republican universe, transforming the state into a bastion of power for their party.

But now, recent surveys showing a tightening presidential race in Florida have given some Democrats glimmers of hope that they could begin to claw their way back into contention in what was once the most contested of all the battleground states.

That movement in public opinion, along with the announcement that Robert F. Kennedy Jr. will appear on the ballot in Florida this fall, has injected a fresh sense of unpredictability into the wild world of the state’s politics. And yet some Democrats are engaging in a kind of political magical thinking, flirting with the notion that small signs of improvements mean the state could turn toward their party once again. The reality is much more sobering: Wresting Florida from Republicans’ grip in key races will be difficult.

Some Democrats see opportunity in state ballot measures that would enshrine abortion rights and legalize marijuana for recreational use, and believe that both issues could boost liberal turnout in November. Others point to President Biden’s growing advantage with seniors, a key demographic group in the state, and to polling that shows Senator Rick Scott, a Republican, facing an increasingly competitive re-election contest.

“Florida is a very tough state for Democrats to win,” said Dan Kanninen, the Biden campaign’s battleground states director. “We know that with eyes wide open, but there are some particular factors this time around that make Florida much more interesting.”

Politically interesting is far from politically competitive. Even with Mr. Kennedy on the ballot, Republicans and Democrats say that his presence is unlikely to be decisive.