Gov. Ron DeSantis of Florida suspended his campaign for president on Sunday, just two days before the New Hampshire primary election, and endorsed former President Donald J. Trump.
It marked a spectacular implosion for a candidate once seen as having the best chance to dethrone Mr. Trump as the Republican Party’s nominee in 2024.
But Mr. DeSantis’s devastating 30-percentage-point loss to Mr. Trump in the Iowa caucuses last Monday had left him facing a daunting question: Why keep going? On Sunday, he provided his answer, acknowledging there was no point in soldiering on.
“I am today suspending my campaign,” Mr. DeSantis said in a video posted after The New York Times reported he was expected to leave the race. “Trump is superior to the current incumbent, Joe Biden. That is clear. I signed a pledge to support the Republican nominee, and I will honor that pledge. He has my endorsement because we can’t go back to the old Republican guard of yesteryear.”
Mr. DeSantis flew home to Tallahassee late Saturday after campaigning in South Carolina. He had been expected to appear at a campaign event in New Hampshire on Sunday afternoon, but one person familiar with the matter said that was no longer the case.
After announcing his run for president in May, Mr. DeSantis’s campaign proved a costly flop, spending tens of millions of dollars in concert with well-funded outside groups to little apparent effect.
Constant mockery from Mr. Trump — about everything from Mr. DeSantis’s facial expressions to his choice of footwear — degraded his image as a confident conservative warrior. Over the course of the campaign, Mr. DeSantis’s national poll numbers fell by roughly half, a seeming indictment of both his skills as a candidate and his strategy of trying to run to Mr. Trump’s right. A vaunted ground game paid for by his super PAC, Never Back Down, hardly seemed to make a dent in the race.
At points, it felt as if Mr. DeSantis was careening from one embarrassment to the next, as his campaign dealt with setbacks like mass layoffs and the fallout from producing a social media video that featured a Nazi symbol.
In Iowa, his brash promise to win proved empty. Instead, he barely beat former Gov. Nikki Haley of South Carolina, whose more moderate image seemed a poor fit for the state’s socially conservative Republicans. Pouring resources into Iowa starved Mr. DeSantis’s efforts in New Hampshire and South Carolina, two of the other early nominating states, where his poll numbers cratered. His loss of support from both voters and donors meant that there was little point in continuing on to more inevitable defeats.
While he had started the year leading Mr. Trump in New Hampshire, polls now showed Mr. DeSantis in a distant third place, drawing around 6 percent of the vote.
Chaos marked the last days of his campaign, just as it had the first, when he kicked off his campaign with a widely mocked and technically marred livestream event on Twitter. Over the weekend, Mr. DeSantis’s schedule was in constant flux, as he flew between New Hampshire and South Carolina with little notice, postponing events and finally canceling his appearances on the Sunday morning political shows.
Last week, Mr. DeSantis had started signaling that he might be looking to exit the race, casting his eyes forward to the 2028 election and conceding that Mr. Trump had won an overwhelming victory in Iowa.
Both Mr. DeSantis and his allies seemed to be running perilously low on money. No pro-DeSantis ad had run on New Hampshire television since before Thanksgiving.