Nikki Haley will suspend her US presidential campaign after being soundly defeated across the country in a series of primary elections on Super Tuesday, sources said.
The move leaves former president Donald Trump as the last remaining major candidate for the 2024 Republican nomination.
Three sources have confirmed Ms Haley’s decision ahead of an announcement scheduled for Wednesday morning, local time.
Ms Haley, a former South Carolina governor and UN ambassador, was Mr Trump’s first significant rival when she jumped into the race in February 2023.
She spent the final phase of her campaign aggressively warning the Republicans against embracing Mr Trump, whom she argued was too consumed by chaos and personal grievance to defeat President Joe Biden in the general election.
Her departure clears Mr Trump to focus solely on his likely rematch in November with Mr Biden. The former president is on track to reach the necessary 1,215 delegates to clinch the Republican nomination later this month.
Ms Haley’s defeat marks a painful, if predictable, blow to those voters, donors and Republican Party officials who opposed Mr 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. It is unclear whether Mr Trump, who recently declared that Ms Haley’s donors would be permanently banned from his movement, can ultimately unify a deeply divided party.
Ms Haley is not planning to endorse Mr Trump in her Wednesday announcement, according to the people with knowledge of her plans.
Instead, she is expected to encourage him to earn the support of the coalition of moderate Republicans and independent voters who supported her.
Ms Haley leaves the 2024 presidential contest having made history as the first woman to win a Republican primary. She beat Mr 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 Mr Trump off his path to a third straight nomination.
President Joe Biden and Mr Trump romped through more than a dozen states on Super Tuesday, all but cementing a rematch in November’s presidential election.
Their victories from coast to coast, including the delegate-rich states of California and Texas, left little doubt about the trajectory of the race.
Ms Haley won Vermont, denying Mr Trump a full sweep, but the former president carried other states that might have been favourable to her such as Virginia, Massachusetts and Maine, which have large swathes of moderate voters like those who have backed her in previous primaries.
Hours after the last polls closed in Alaska, Ms Haley scheduled a 10am ET (3pm GMT) speech in her home state of South Carolina to announce she was suspending her campaign.
The only contest Mr Biden lost Tuesday was the Democratic caucus in American Samoa, a tiny U.S. territory in the South Pacific Ocean. Mr Biden was defeated by previously unknown candidate Jason Palmer, 51 votes to 40.
Not enough states will have voted until later this month for Mr Trump or Mr Biden to formally become their parties’ presumptive nominees.
But the primary’s biggest day made their rematch a near-certainty. Both the 81-year-old Mr Biden and the 77-year-old Mr Trump continue to dominate their parties despite facing questions about their age, and neither having broad popularity across the general American electorate.