Trump is the overwhelming front-runner in South Carolina. Here’s the latest.

The polls are now closed in the South Carolina Republican primary and results should start flowing in momentarily.

Former President Donald J. Trump is widely expected to notch another decisive victory over his last major primary rival, Nikki Haley, as he continues his march toward securing the Republican Party nomination for president.

As voters flowed into polling stations in Ms. Haley’s home state earlier in the day, Mr. Trump was more than 500 miles away, near Washington, delivering what was at times a rambling speech at the Conservative Political Action Conference, known as CPAC. In a straw poll of conference-goers, Gov. Kristi Noem of South Dakota and Vivek Ramaswamy tied as the top choice to be Mr. Trump’s running mate.

Mr. Trump, looking past Ms. Haley to the general election, barely mentioned South Carolina during his speech, but he headed to the state afterward. He is set to attend an election-night watch party in Columbia, the capital.

Ms. Haley’s election-night watch party will be in Charleston, concluding her “Beast of the Southeast” bus tour across the state. She had been on a furious drive of campaigning in South Carolina this week and voted earlier in the day in Kiawah Island.

Here’s what else to know:

• Ms. Haley says she will stay in the race regardless of Saturday’s outcome. Bolstered by a cash influx that is keeping her long-shot campaign afloat, Ms. Haley, an ambassador to the United Nations under Mr. Trump, has pledged in stump speeches and interviews to campaign through Super Tuesday, on March 5.

• On Friday, Ms. Haley’s campaign manager announced a seven-figure ad buy to run in an unspecified number of the 15 Super Tuesday states, where 874 Republican delegates are up for the taking.

• Palmetto State voters have long been heralded as deciders of presidential primaries — Republican candidates who have won here have gone on to clinch their party’s nomination in 10 of the last 11 presidential cycles. But this year, the dynamics of the Republican primary have diminished the state’s bellwether status. Most polls have shown Mr. Trump trouncing Ms. Haley by more than 20 points.

Jazmine Ulloa, Neil Vigdor and Maya King contributed reporting.