MIAMI — Representative Charlie Crist, Democrat of Florida, entered the race for governor on Tuesday, becoming the first challenger to Ron DeSantis, a Republican who raised his profile during the pandemic and is now one of the best-known governors in the country and a leading contender for his party’s presidential nomination in 2024.

“Today, Florida has a governor that’s only focused on his future, not yours,” Mr. Crist said in a video posted on Twitter, ahead of a planned announcement later in the morning in his hometown of St. Petersburg.

Mr. Crist has a long political history in Florida and is widely known throughout the state. He served as governor as a Republican from 2007 to 2011 before running unsuccessfully for the U.S. Senate as an independent, losing to Marco Rubio. After switching parties, he later lost a Democratic bid for governor in 2014 against the incumbent, Rick Scott.

But Mr. Crist’s experience is unlikely to deter other Democratic candidates. His clout has been diminished by years of electoral failures and by a party that is increasingly open to a wider range of more diverse public figures to be its standard bearers. Two women, Agriculture Commissioner Nikki Fried and Representative Val Demings of Orlando, are considering their own Democratic runs for the governor’s mansion.

In advance of Mr. Crist’s announcement, Mr. DeSantis held an official event Monday in St. Petersburg, touting the wins he racked up during the annual legislative session that concluded last week — a session that he and Republicans in control of the Legislature used to champion policies that will appeal to Florida’s increasingly conservative electorate.