West Virginia Gov. Jim Justice filed paperwork for a Senate run on Thursday and is expected to make an official announcement Thursday evening. If he wins the nomination, he’d take on Democratic Sen. Joe Manchin in what will likely be one of the most hotly contested and closely watched Senate contests in the country.

Justice is a well-liked and wealthy coal magnate who is an ally to former President Donald Trump, and Republicans believe his campaign kickoff goes a long way toward retaking the Senate next year. Trump won the state by 39 percentage points in 2020, and the Mitch McConnell-aligned Senate Leadership Fund recently commissioned a poll showing Justice is the strongest candidate against Manchin.

Justice is set to make remarks this evening at The Greenbrier, his luxury resort in White Sulphur Springs, W.Va.

Manchin has said he will not decide whether he will run for reelection until the end of the year. He has also left the door open to a presidential bid.

The National Republican Senatorial Committee played an active role in recruiting Justice. With a 64 percent approval rating, Justice is the fifth-most popular governor in the country, according to a survey conducted last year by Morning Consult.

Before taking on Manchin, Justice must face GOP Rep. Alex Mooney in the Republican primary. The conservative group Club for Growth has vowed to spend at least $10 million on the race, and has already reported spending from its super PAC this week.

The congressman is launching an TV ad on Thursday that bashes Justice as a “liberal.”

Justice was previously registered as a Democrat and switched parties in 2017. Both Justice and Mooney are pursuing Trump’s endorsement.

POLITICO previously reported that Justice planned to launch his campaign on Thursday.