May 1, 2022 - Democratic Sen. Joe Manchin appears to be taking sides in the bitter Republican primary in his home state of West Virginia that pits US Rep. David McKinley against Trump-backed Rep. Alex Mooney.

In a 30-second video ad released Friday, Manchin says: "Alex Mooney has proven he's all about Alex Mooney. But West Virginians know David McKinley is all about us."

McKinley and Mooney are facing off in the May 10 Republican primary for West Virginia's 2nd Congressional District after the state lost a seat in redistricting following the 2020 census.

Former President Donald Trump endorsed Mooney last year after he voted against a $1.2 trillion bipartisan infrastructure bill, which was a key part of President Joe Biden's economic agenda. McKinley voted for the infrastructure package, which Biden later signed into law.

In the ad, Manchin accuses Mooney and his "out-of-state supporters" of suggesting McKinley supported Biden's sweeping Build Back Better plan, saying it was an "outright lie."

"David McKinley has always opposed reckless spending because it doesn't make sense for West Virginia," says Manchin, who also did not support the President's climate and social spending plan.

McKinley's campaign posted the video on the GOP fundraising platform WinRed, writing, "Joe Manchin knows that I've always fought wasteful spending and opposed liberal policies that don't work for West Virginians."

CNN has reached out to McKinley's campaign for comment.

Asked if Manchin was endorsing McKinley, the senator's spokesperson Sam Runyon told CNN that the "ad speaks for itself."

Mooney shared the ad on Twitter on Saturday, writing: "Further proof David McKinley is a complete and total RINO. Democrat Joe Manchin is endorsing him."

Mooney has outraised McKinley this cycle, hauling in $3.7 million to his opponent's $2 million through April 20, per their pre-primary filings with the Federal Election Commission.

The winner would be the overwhelming fa`vorite in the general election for the 2nd Congressional District, which covers the northern half of the state and would have backed Trump by 37 points in 2020.

Manchin, who isn't up for reelection until 2024, is the lone Democrat representing the Mountain State in Congress. He has a history of across-the-aisle endorsements. Last year, he chose to back Alaska GOP Sen. Lisa Murkowski's 2022 reelection bid, and he supported Maine Republican Sen. Susan Collins in 2020.

The West Virginia GOP race is just one of several member-versus-member primaries this year because of redistricting. Later this month, Georgia Democrats Carolyn Bourdeaux and Lucy McBath will face off for a suburban Atlanta seat. Illinois is hosting two such primaries in June: Democrats Sean Casten and Marie Newman are both running for a suburban Chicago seat while Republicans Rodney Davis and Mary Miller are vying for a redrawn Central Illinois district. And in Michigan, Democrats Andy Levin and Haley Stevens are both seeking the same suburban Detroit seat.