Donald Trump has won South Carolina’s Republican primary, beating former UN ambassador Nikki Haley in her home state and further consolidating his path to a third straight GOP nomination.

Trump has now swept every contest that counted for Republican delegates, with wins already in Iowa, New Hampshire, Nevada and the US Virgin Islands. The former president’s latest victory will likely increase pressure on Haley, who was Trump’s former representative to the UN and South Carolina governor from 2011 to 2017, to leave the race.

A 2020 general rematch between Trump and President Joe Biden is becoming increasingly inevitable. Haley has vowed to stay in the race through at least the batch of primaries on March 5, known as Super Tuesday, but was unable to dent Trump’s momentum in her home state despite holding far more campaign events and arguing that the indictments against Trump will hamstring him against Biden.

The Associated Press (AP) declared Trump the winner as polls closed statewide at 7pm, local time. The AP based its race call on an analysis of AP VoteCast, a comprehensive survey of Republican South Carolina primary voters. The survey confirms the findings of pre-election day polls showing Trump far outpacing Haley statewide.

South Carolina’s first-in-the-South primary has historically been a reliable bellwether for Republicans. In all but one primary since 1980, the Republican winner in South Carolina has gone on to be the party’s nominee. The lone exception was Newt Gingrich in 2012.

Haley said in recent days that she would head straight to Michigan for its Tuesday primary, the last major contest before Super Tuesday. She faces questions about where she might be able to win a contest or be competitive.

Republican presidential candidate former UN Ambassador Nikki Haley greets a supporter after voting in Kiawah Island, South Carolina. Photo / AP

Trump and Biden are already behaving like they expect to face off in November.

Trump and his allies argue Biden has made the US weaker and point to the chaotic withdrawal from Afghanistan and Russia’s decision to launch a full-scale invasion of Ukraine. Trump has also repeatedly attacked Biden over high inflation earlier in the president’s term and his handling of record-high migrant crossings at the US-Mexico border.

Trump has questioned, often in harshly personal terms, whether the 81-year-old Biden is too old to serve a second term. Biden’s team in turn has highlighted the 77-year-old Trump’s own flubs on the campaign trail.

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Biden has stepped up his recent fundraising trips around the country and increasingly attacked Trump directly. He’s called Trump and his “Make America Great Again” movement dire threats to the nation’s founding principles and the president’s re-election campaign has lately focused most of its attention on Trump, suggesting he’d use the first day of a second presidency as a dictator and that he’d tell Russia to attack Nato allies who fail to keep up with defence spending obligations mandated by the alliance.

Haley also criticised Trump on his Nato comments and also for questioning why her husband wasn’t on the campaign trail with her - even as former first lady Melania Trump hasn’t appeared with him. Major Michael Haley is deployed in the Horn of Africa on a mission with the South Carolina Army National Guard.

But South Carolina’s Republican voters line up with Trump on having lukewarm feelings about Nato and continued US support for Ukraine, according to AP VoteCast data from today’s primary. About six in 10 oppose continuing aid to Ukraine in its fight against Russia. Only about a third described America’s participation in Nato as “very good”, with more saying it’s only “somewhat good”.

Mike Schmidt votes on the morning of the South Carolina Republican primary at Cayce United Methodist Church in Cayce, South Carolina. Photo / AP

Haley has raised copious amounts of campaign money and was scheduled to begin a cross-country campaign swing on Sunday in Michigan ahead of Super Tuesday on March 5, when many delegate-rich states hold primaries.

But it’s unclear how she can stop Trump from clinching enough delegates to become the party’s presumptive nominee for the third time.

Senator Lindsey Graham, the Republican senator for South Carolina, complimented Haley while speaking to reporters at Trump’s election night party in Columbia but suggested it was time for her to drop out.

“I think the sooner she does, the better for her, the better for the party,” Graham said.

Trump’s political strength has endured despite facing 91 criminal charges related to his efforts to overturn his 2020 election loss to Biden, the discovery of classified documents in his Florida residence and allegations that he secretly arranged payoffs to a porn actress.

The former president’s first criminal trial is set to begin on March 25 in New York, where he faces 34 counts of falsifying business records related to hush money paid to porn star Stormy Daniels in the closing weeks of his 2016 presidential campaign.

Biden won South Carolina’s Democratic primary earlier this month and faces only one remaining challenger, Dean Phillips. The Minnesota Democratic congressman has continued to campaign in Michigan ahead of the Democratic primary there, despite having little chance of actually beating Biden.

Though Biden is expected to cruise to his party’s renomination, he faces criticism from some Democrats for providing military backing to Israel in its war against Hamas in Gaza. Some in his party support a ceasefire as the death toll in Israel’s war has reached 30,000 people, two-thirds of them women and children. The war could hurt the president’s general election chances in swing states like Michigan, which is home to a large Arab-American population.