Trump Is Said to Intend to Campaign for South Carolina Governor in GOP Runoff

WASHINGTON — President Donald Trump intends to campaign Monday for Gov. Henry McMaster of South Carolina, according to Republican officials familiar with the plan, putting his presidential prestige on the line for one of his earliest supporters a day before the state’s closely contested Republican runoff election.

In a gamble that he can lift McMaster to the nomination at the eleventh hour, Trump intends to join McMaster for a rally in the Columbia area hours before the polls open in the state.

And this Saturday, Vice President Mike Pence will campaign with McMaster, who is locked in a close race for the Republican nomination with John Warren, a former Marine and political newcomer.

The White House’s last-minute intervention amounts to political payback for the governor, who was among the first statewide Republican elected officials to support Trump. McMaster has been an outspoken ally of the president ever since. He has argued that Trump should receive a Nobel Peace Prize for his negotiations with North Korea, and this week he defended Trump’s hard line on immigration and the separation of children from their families at the border.

McMaster talked by telephone with Trump on Monday and asked him to come to the state, according to Republican officials who spoke on the condition of anonymity to discuss plans that have not yet been made public. They said the president felt he needed to demonstrate his loyalty to the governor.

The president may be feeling confident about his clout among South Carolina’s Republican voters, who ousted a vocal critic of his, Rep. Mark Sanford, in the primary last week. Trump attacked Sanford and endorsed his opponent, Katie Arrington, in a primary day Twitter post.

Yet by flying into South Carolina the day before an uncertain vote, Trump is also risking embarrassment in a state that he carried by 14 points in 2016.

McMaster, 71, fell short of winning a majority in the primary this month, in part because he is identified with a political status quo at the state Capitol that has become an easy target amid an open corruption investigation that has led to a series of indictments of Republican lawmakers. And in Warren, a 39-year-old businessman, the governor is facing an opponent with no voting record to pick apart.

McMaster has scrambled to slow Warren during the two-week runoff, reminding voters of his support from Trump, but Warren has received endorsements from the other two leading Republicans who also ran in the primary race.

This is not Trump’s first gamble in a Republican nominating contest. At the urging of a host of senators last year, he went to Alabama to rally support for Sen. Luther Strange during the special election there. But Trump was stung when Roy S. Moore easily defeated Strange in the runoff.

As in Alabama, where the Senate seat was left vacant after Jeff Sessions became the attorney general, there is a competitive race in South Carolina because of an administration appointment: McMaster took office last year when Nikki R. Haley, then the governor, become the U.S. ambassador to the United Nations.