Three people with direct knowledge who spoke on the condition of anonymity because they were not authorised to speak publicly confirmed Haley’s decision before an announcement by her on Wednesday morning.

Haley, a former South Carolina governor and UN ambassador, was Trump’s first significant rival when she jumped into the race in February 2023.

She spent the final phase of her campaign aggressively warning Republicans against embracing Trump, whom she argued was too consumed by chaos and personal grievance to defeat President Joe Biden in the general election.

Her departure clears Trump to focus solely on his likely rematch in November with Biden.

The former president is on track to reach the necessary 1215 delegates to clinch the Republican nomination later in March.

Haley’s defeat marks a painful, if predictable, blow to those voters, donors and Republican Party officials who opposed Trump and his fiery brand of “Make America Great Again” politics.

She was especially popular among moderates and college-educated voters, constituencies that will likely play a pivotal role in the general election.

Haley would not announce an endorsement on Wednesday, the Wall Street Journal reported, but would encourage Trump to earn the support of Republican and independent voters who backed her.

Haley leaves the 2024 presidential contest having made history as the first woman to win a Republican primary.

She beat Trump in the District of Columbia on Sunday and Vermont on Tuesday.

She had insisted she would stay in the race through Super Tuesday and crossed the country campaigning in states holding Republican contests.

Ultimately, she was unable to knock Trump off his glide path to a third straight nomination.

Haley had initially ruled out running against Trump in 2024. But she changed her mind and ended up launching her bid three months after he did, citing among other things the country’s economic troubles and the need for “generational change”.

Haley, 52, later called for competency tests for politicians over the age of 75 – a knock on both Trump, who is 77, and President Joe Biden, who is 81.

Her candidacy was slow to attract donors and support, but she ultimately outlasted all of her other Republican rivals, including Florida Governor Ron DeSantis, former vice-president Mike Pence and senator Tim Scott.

She gained popularity with many Republican donors, independent voters and the so-called “Never Trump” crowd, even though she criticised the criminal cases against him as politically motivated and pledged that, if president, she would pardon him if he were convicted in federal court.

Haley has made clear she does not want to serve as Trump’s vice-president or run on a third-party ticket arranged by the group No Labels.

She leaves the race with an elevated national profile that could help her in a future presidential run.

– AAP