Florida Governor Ron DeSantis, once viewed as the Republicans' best shot at moving past Donald Trump, has dropped out of the 2024 presidential race and endorsed the former president.
The Republican hoped he would emerge as a serious challenger to Mr Trump but his White House bid failed to meet expectations.
The announcement comes on the eve of the New Hampshire primary on Tuesday.
Mr DeSantis said in a post on X: "It's clear to me that a majority of Republican primary voters want to give Donald Trump another chance."
“Success is not final, failure is not fatal: it is the courage to continue that counts.”
- Winston Churchill pic.twitter.com/ECoR8YeiMm
— Ron DeSantis (@RonDeSantis) January 21, 2024
Early primary polls suggested Mr DeSantis was in a strong position to take on Mr Trump.
He came to the position as a hard-right campaigner with “anti-woke” values and with a record of voting down LGBT, abortion, and gun control policies
But Mr DeSantis struggled to find his footing in the primary.
A high-profile announcement was plagued by technical glitches and there were constant upheavals to his staff and campaign strategy.
He lost the Iowa caucuses, which he had vowed to win, by 30 percentage points to Mr Trump.
Mr DeSantis had launched his campaign for the Republic nomination with a Twitter video alongside Elon Musk.
He recently made headlines after clashing with Disney over its plans to build a new corporate campus in Orlando.
Just one Republican candidate remains to challenge Mr Trump for his party's nomination in the November US election.
Nikki Haley is the former president's sole challenger.
More than 70 per cent of Republicans have a favorable opinion of Trump, according to most opinion polls.
The winner of this year's Republican nominating contests will take on President Joe Biden, the likely Democratic nominee.