Former South Carolina Governor Nikki Haley will suspend her presidential campaign on Wednesday, according to a source familiar with her plans.

This will ensure that Donald Trump wins the Republican nomination and once again faces Democratic President Joe Biden in his November bid.

The source said Ms Haley would give a speech at 10 a.m. local time (1500 GMT) to discuss her future in the race, but she would not make an endorsement at that time.

She will urge Mr Trump to try to win the backing of her supporters, which include a significant chunk of moderate Republicans and independent voters, the source added.

The source said Ms Haley, who served as Mr Trump’s ambassador to the United Nations when he was president, would discuss the importance of a robust foreign policy.

Throughout her campaign, Ms Haley said the United States must help Ukraine defend itself against Russian aggression, a position at odds with Trump.

There was no indication Mr Trump would moderate his message.

“He’ll continue to focus on the issues that matter: immigration, economy, foreign policy,” Karoline Leavitt, press secretary for the Trump campaign, said late on Tuesday.

On Tuesday, known as Super Tuesday, Mr Trump beat her soundly in 14 of the 15 Republican nominating contests.

Ms Haley lasted longer than any other Republican challenger to Trump but never posed a serious threat to the former president, whose iron grip on the party’s base remains firm despite his multiple criminal indictments.

Few Americans want the rematch between Trump, 77, and Biden, 81—the first repeat U.S. presidential contest since 1956.

Opinion polls show both Biden and Trump have low approval ratings among voters.

The election promises to be deeply divisive in a country already riven by political polarisation.

Mr Biden has cast Mr Trump as an existential danger to democratic principles, while Trump has sought to re-litigate his false claims that he won in 2020.

Mr Haley, 52, had drawn support from deep-pocketed donors intent on stopping Mr Trump from winning a third consecutive Republican presidential nomination, particularly after she notched a series of strong performances at debates that Trump opted to skip.

She failed to pry loose enough conservative voters in the face of Trump’s dominance.

But her stronger showing among moderate Republicans and independents – she won unaffiliated voters by a wide margin in New Hampshire and notched almost 40 per cent of the vote in South Carolina – highlighted how Trump’s scorched-earth style of politics could make him vulnerable in the November 5 election.

On March 3, she won the Washington, D.C., Republican primary with 62.9 per cent of the vote, versus 33.2 per cent for Trump. On Tuesday, her only win came in Vermont, a small, deeply Democratic state.

Mr Biden has his baggage, including widespread concern about his age.

Three-quarters of respondents in a February Reuters/Ipsos poll said he was too old to work in government after already serving as the oldest U.S. president in history.

About half of respondents said the same about Mr Trump.

(Reuters/NAN)