MANCHESTER, N.H. — Sen. Tim Scott, South Carolina Republican who ran for the GOP nomination, will endorse former President Donald Trump Friday night at a campaign rally in Concord, slighting his former governor and Mr. Trump’s chief Granite State rival, Nikki Haley.

Mr. Scott dropped out of the presidential race in November.

He’ll join a growing list of House and Senate Republicans lining up behind Mr. Trump, the prohibitive favorite to win the nomination.

Florida’s two GOP senators, Rick Scott and Marco Rubio, snubbed their own governor, Ron DeSantis, the only other Republican left in the race, in favor of Mr. Trump.

The former president leads in the polls going into Tuesday’s New Hampshire primary by 16 points over Ms. Haley. That’s much closer than in Iowa, where Mr. Trump won the caucuses by 30 points and swept all but one of the state’s 99 counties.

Tim Scott is becoming the third former presidential candidate to endorse Mr. Trump. Biotech tycoon Vivek Ramaswamy, who dropped out of the race after a fourth-place finish in Iowa, endorsed the former president at a New Hampshire rally Monday. North Dakota Gov. Doug Burgham, who dropped out of the race in December, endorsed Mr. Trump last week.

• Susan Ferrechio can be reached at sferrechio@washingtontimes.com.