Florida’s Democratic agricultural commissioner, Nikki Fried, announces her bid for governor.

MIAMI — Nikki Fried, Florida’s agriculture commissioner, declared her candidacy for governor on Tuesday, casting herself as the Democratic Party’s best option to defeat Ron DeSantis, the popular Republican incumbent, given her role as the only statewide elected Democrat.

“After two decades of Republican governors, it’s time to try something new,” Ms. Fried said in a brief phone interview days before her announcement. “It’s time for a change.”

Ms. Fried is the second major Democrat to enter the race. Representative Charlie Crist of St. Petersburg began his campaign last month and has been holding political events across the state. Mr. Crist is far better known: He served as Florida’s Republican governor from 2007 to 2011, lost a Senate run as an independent in 2012 and ran unsuccessfully against Gov. Rick Scott in 2014 as a Democrat.

Ms. Fried, who was elected in 2018, acknowledged that Mr. Crist would start the race with better name recognition, but said she had “no doubt” that Democratic voters would be hungry for a fresh alternative.

Before winning the 2018 election by just 6,753 votes, Ms. Fried, 43, worked as a Fort Lauderdale-based lawyer and medical marijuana lobbyist. She boasts that she holds both a medical marijuana card and a concealed-weapons permit.

The governor’s contest in the nation’s third-largest state began early, as Democrats hope to stall the political career of Mr. DeSantis, who is widely seen as a possible presidential contender in 2024 if he wins re-election next year. He has recently traveled to speak at political events in Pennsylvania and Texas.

Representative Val Demings of Orlando had also been seen as a likely Democratic challenger to Mr. DeSantis. But she is set to announce a campaign against Senator Marco Rubio instead, a move that has scrambled plans for other Democrats down the ballot. Representative Stephanie Murphy of Winter Park decided against a Senate run after Ms. Demings’s decision became public.

State Senator Annette Taddeo of Miami, who was Mr. Crist’s running mate in 2014, is still weighing a candidacy for governor.

“I will continue meeting with supporters across the state to assess the best path for me to do the most good for the people of Florida,” Ms. Taddeo said in a statement last week.