Ron DeSantis, the pugnacious 44-year-old governor of Florida who has championed conservative causes and thrown a yearslong flurry of punches at America’s left, entered the presidential race on Wednesday, giving Donald J. Trump the most formidable Republican rival he has faced since his ascent in 2016.
Mr. DeSantis filed paperwork declaring his candidacy with the Federal Election Commission hours before a planned livestream announcement on Twitter with the platform’s owner, Elon Musk — a potential online spectacle with little precedent in American presidential politics. The governor’s willingness to tie his announcement to an eccentric billionaire like Mr. Musk suggests an appetite for risk and a desire to maximize media attention.
The entry of Mr. DeSantis comes at a pivotal moment for the Republican Party, which must choose between aligning once more behind Mr. Trump — who lost in 2020 and continues to rage falsely about a stolen election — or uniting around a new challenger to take on President Biden.
Even though Mr. DeSantis has slipped well behind Mr. Trump in national polls in recent months, he retains a host of strengths: a mountain of cash, a robust campaign operation and a series of conservative policy victories in Florida after a landslide re-election triumph last fall.
The governor, who rose to national prominence with his restriction-averse handling of the coronavirus pandemic, argues that his “Florida Blueprint” can be a model for reshaping the United States in a starkly conservative mold, especially on social issues.
He now confronts the daunting endeavor of toppling a former president whose belligerence and loyal base of support have discouraged most leading Republicans — including, up to now, Mr. DeSantis — from making frontal attacks against him. Mr. Trump, who has a mounting list of legal troubles, clearly sees Mr. DeSantis as a political threat and has unloaded on him for months, mocking him as “Ron DeSanctimonious” and slamming his stewardship of Florida.
“Trump is not as invincible as he once seemed and DeSantis is a serious contender,” said Mike Murphy, a veteran Republican strategist. “There are Republican voters looking for someone who can move beyond Trump, someone who can fight the liberals but also win elections. That’s the space DeSantis is trying to inhabit.”
Mr. DeSantis’s chances of capturing the nomination may depend on whether the Republican primary becomes a crowded, Trump-dominated food fight — something similar to what unfolded in 2016 — or if he can turn the contest into a two-man race.
The Republican field has slowly ballooned and to winnow the field back down Mr. DeSantis is likely to need strong showings in Iowa and New Hampshire, the first two nominating states, with anti-Trump voters coalescing around him.
A key focus of the primary, and the general election should Mr. DeSantis make it that far, will be his record as governor. He and a pliant Florida Legislature have passed contentious laws that have excited the right and angered many Democrats, including Black and L.G.B.T.Q. people, students and abortion rights supporters in Florida.
Mr. DeSantis does not always give the appearance of a skilled retail politician. As he ramped up his preparations this year with a book tour and a foreign trade mission, he seemed to struggle at points. Awkward moments on the road — including cringeworthy facial expressions that quickly became memes — generated negative headlines. So did some poorly calculated policy pronouncements, particularly his declaration that defending Ukraine from the Russian invasion was not a vital U.S. interest.
Some major donors who once saw him as the most suitable Trump challenger backed away, citing fears that the heightened scrutiny was exposing his flaws as a candidate.
In recent weeks, however, Mr. DeSantis has seemed to recover, hitting back with more force against Mr. Trump. He has criticized the former president for not endorsing a six-week abortion ban signed in Florida and has described a “culture of losing” that he says took hold of the Republican Party under Mr. Trump’s leadership. He also told donors in a private call that Mr. Trump could not beat Mr. Biden in a general election. And a pro-DeSantis super PAC says it will deploy roughly $200 million in support of him.
The governor could also soon sign an elections bill that clears up a potential legal roadblock to his candidacy. Florida’s so-called resign-to-run statute could have compelled Mr. DeSantis to resign if he sought the presidency, although the legal questions surrounding the rule have never been settled.
But state lawmakers clarified the law’s language late last month so that it no longer applies to elected officials running for president or vice president.
In addition to the announcement on Twitter, the DeSantis campaign had discussed holding an in-person rally next week in Dunedin, Fla., a suburb of Tampa where the governor was raised. But the campaign recently decided against that in favor of visits to early nominating states, according to a person familiar with the discussions.
Mr. DeSantis’s supporters say announcing his candidacy will allow him to make a more direct case against Mr. Trump, and will open the floodgates of an aggressive fund-raising push.
“Major donors have been waiting for DeSantis to get in the race,” said Roy Bailey, a Texas businessman and longtime fund-raiser for Mr. Trump who is now set to back Mr. DeSantis. “What he’s done in Florida has been a beacon of conservative leadership for the rest of the country.”
Jonathan Swan contributed reporting.