Gov. Jim Justice of West Virginia is set to announce a Senate campaign on Thursday, giving Republicans a strong recruit against Senator Joe Manchin III, one of the most vulnerable Democrats up for re-election in 2024.
The West Virginia race is one of the most essential pickup opportunities for Republicans if they are to retake control of the Senate, which Democrats hold by a narrow 51-49 seat margin.
Mr. Manchin, who represents by far the most Republican state held by any Democratic senator, has yet to announce whether he will seek re-election, but Republicans are hoping that Mr. Justice’s entry might spur him toward retirement.
Mr. Manchin in recent years has been one of the few Democrats who can compete in the overwhelmingly Republican state.
Mr. Justice’s team teased a “special announcement” at 5 p.m. Eastern time on Thursday at the Greenbrier Resort in White Sulphur Springs, W.Va. It made a point to note that his English bulldog — Babydog, known for a memorable appearance last year at Mr. Justice’s State of the State speech — would be present for the announcement.
The advisory did not specify the nature of the announcement, though it offered a livestream link to a YouTube page with the description “The official YouTube channel for Jim Justice for U.S. Senate, Inc.” Two people with knowledge of Mr. Justice’s plans confirmed he would be entering the Senate race.
Before facing Mr. Manchin, Mr. Justice would need to make it through a Republican primary. He will have at least one major opponent, Representative Alex Mooney, who has been closely allied with former President Donald J. Trump.
Mr. Mooney has already attacked Mr. Justice as a “RINO,” or “Republican in name only,” one of Mr. Trump’s and his allies’ favorite insults.
Mr. Mooney has the backing of the Club for Growth, the influential conservative group that has spent heavily in recent Republican primaries, and Senator Ted Cruz, Republican of Texas, endorsed him last week.
Mr. Justice, a billionaire businessman, was first elected governor in 2016 and re-elected in 2020, making him term-limited next year. He initially ran and won as a Democrat, but switched his party affiliation to Republican in 2017, less than a year into his first term.
He made that announcement at a rally alongside Mr. Trump, saying, “Today I will tell you as West Virginians that I can’t help you anymore being a Democrat governor.” As is traditional for politicians who switch allegiances, he said his former party had moved away from him, not the other way around.
Top Senate Republicans have been eager to lure Mr. Justice into the race. One Nation, a nonprofit group aligned with Senator Mitch McConnell, the Republican leader, recently began a $1 million ad campaign against Mr. Manchin for his support of President Biden’s Inflation Reduction Act.
Mr. Manchin appeared on Fox News this week, in an interview with Sean Hannity, and attacked the Biden administration for the way it had implemented the legislation. He even threatened to vote to repeal it over its climate provisions.
Mr. Hannity asked why Mr. Manchin had remained with the Democratic Party.
“Well, they don’t always get my vote, you know that — if I can’t go home and explain, I don’t vote for it,” Mr. Manchin said. “I think about that every day: Why am I a Democrat?”
Shane Goldmacher contributed reporting.
