Florida Governor Ron DeSantis ended his fading presidential campaign on Sunday and endorsed Donald Trump just two days before the pivotal New Hampshire primary, leaving former U.N. Ambassador Nikki Haley as Trump’s last long-shot challenger for the Republican nomination.

DeSantis’ decision, less than a week after his deflating loss to Trump in Iowa despite an enormous investment there, caps a stunning fall from grace after DeSantis had been widely seen as Republicans’ most promising alternative to Trump ahead of the general election in November.

His departure sets up the one-on-one battle that Haley has coveted against Trump, the former president who has maintained an iron grip on the Republican electorate despite facing four criminal prosecutions. Trump has pleaded not guilty in all the cases.

But DeSantis’ supporters appear more likely to switch allegiance to Trump than to the more moderate Haley. In New Hampshire, about two-thirds of DeSantis backers cite Trump as their second choice, said Andrew Smith, director of the University of New Hampshire Survey Center.

In a video posted on X, DeSantis endorsed Trump while delivering a parting shot at Haley. “He has my endorsement because we can’t go back to the old Republican guard of yesteryear: a re-packaged form of warmed-over corporatism that Nikki Haley represents,” DeSantis said.

At a Sunday evening rally in Rochester, New Hampshire, Trump - who spent much of last year attacking DeSantis - praised the governor and said he was looking forward to working together to defeat President Joe Biden, the presumptive Democratic nominee.

Trump accused Haley of forming an “unholy alliance” with liberals, never-Trumpers and RINOs, or Republicans in Name Only, to try and win the New Hampshire primary, and repeated a false claim that registered Democrats were allowed to vote in the Republican primary.

Trump holds a double-digit lead over Haley in New Hampshire, according to polls, and his campaign hopes a second consecutive win will make his eventual nomination all but inevitable.

He also has a commanding lead in South Carolina, which votes on Feb. 24. A Haley loss in her home state - where she served as governor from 2011 to 2017 - would likely doom her campaign.

At a campaign event in Seabrook, New Hampshire, Haley drew cheers when she announced that DeSantis had dropped out.

“For now, I’ll leave you with this: May the best woman win,” she said.

David Kochel, a Republican strategist who has worked on five presidential campaigns, said DeSantis’ exit was unlikely to change the basic contours of the campaign, given that his support had cratered.

“The race needs a big dynamic shift, and I don’t feel that DeSantis dropping out is that big a deal as he didn’t have that much going on in New Hampshire, and he didn’t even have that much going on in South Carolina,” he said.

Another Republican consultant, Ford O’Connell, who has ties to both the Trump and DeSantis camps, said he expected most DeSantis voters to “come home” to Trump.

“Without question, Trump is the beneficiary of DeSantis ending his campaign,” he said. With time running short, Haley has sharpened her attacks on the frontrunner in the final days before the election, blaming Trump for Republican electoral losses in 2020 and 2022 and criticizing his praise for authoritarian leaders.

Once a contender

Early last year, DeSantis was considered a top presidential contender and a natural heir to Trump due to his combative style and deeply conservative views. He led several head-to-head polls against Trump.

But his support had declined for several months, due to a flawed campaign strategy, his seeming lack of ease with voters on the campaign trail and Trump’s so far unshakeable command of much of the party’s base.

More than 70% of Republicans have a favourable opinion of Trump, according to most polls. That forced DeSantis to try and appeal to voters who still admired Trump, as well as those who passionately disliked him.

DeSantis failed on both counts. He never successfully articulated to most Trump supporters why he was a better option, while Republicans looking to ditch the former president split their votes among multiple candidates.

While many major donors threw their support behind DeSantis early on, they began to rebel as early as the summer.

Several DeSantis allies say the governor waited too long to enter the race, which left him open to blistering attacks by Trump, who had announced his campaign more than six months earlier.

When DeSantis did formally launch his White House run in May 2023, it was a glitch-filled disaster on Twitter, now known as X, an inauspicious start for a campaign predicated on the governor’s executive competence.

The campaign overhired, burning through cash at a rapid rate, and then outsourced much of the traditional work of a campaign to an outside super PAC, which can accept donations of unlimited size but cannot coordinate with the campaign itself.