Sen. Joe Manchin, D-W.Va., appeared in a Republican primary ad defending Rep. David McKinley, R-W.Va., from accusations that he supported President Biden's Build Back Better agenda.

"I have always said, if I can't go home and explain it, I can't vote for it, and that's why I opposed Build Back Better," Manchin said in a 30-second spot this weekend. 

Manchin went on to defend McKinley against a claim from his Republican opponent, Alex Mooney, who accused McKinley of effectively supporting Build Back Better by voting for the $1.2 trillion infrastructure bill

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"For Alex Mooney and his out-of-state supporters to suggest David McKinley supported Build Back Better is an outright lie," the Democrat said. "David McKinley has always opposed reckless spending because it doesn't make sense for West Virginia."

Joe Manchin

Sen. Joe Manchin speaks at a press conference outside his office on Capitol Hill on Oct. 06, 2021. (Anna Moneymaker/Getty Images)

"Alex Mooney has proven he's all about Alex Mooney," Manchin concluded. "But West Virginians know David McKinley is all about us."

Both Mooney and McKinley are currently in the House of Representatives, but the new congressional maps put McKinley, who represents West Virginia's 1st Congressional District, in the state's 2nd Congressional District, where Mooney is the incumbent. Both announced their races to represent the same district in Oct. 2021.

Mooney accused McKinley of helping grease the skids for Build Back Better in Nov. 2021. He noted that Biden's "NON-infrastructure" package would not have passed the House without the 13 Republicans who voted for it. (Many critics claimed that traditional infrastructure made up a small percentage of the bill.)

Rep. David McKinley

Rep. David McKinley gestures during his town hall meeting at Shepherd University in Shepherdstown, West Virginia, on April 25, 2022. (Bill Clark/CQ-Roll Call, Inc via Getty Images)

While Mooney did not name McKinley in his video, he argued that Republicans who voted for the infrastructure package "have now paved the way for Democrats to pass President Biden's socialist Build Back Better plan."

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McKinley did not vote for the Build Back Better bill, however, which Manchin effectively blocked late last year. 

Former President Trump has backed Mooney in the race, as have Reps. Lauren Boebert, R-Colo., and Ronny Jackson, R-Texas, along with the Club for Growth, FreedomWorks, and the American Conservative Union.

Rep. Alex Mooney

Rep. Alex Mooney offers remarks at a press conference outside the US Capitol on May 20, 2021. (Credit: Rod Lamkey/CNP/Sipa USA)

Former Secretary of State Mike Pompeo endorsed McKinley, however, along with Manchin, Republican West Virginia Gov. Jim Justice, Andrew Yang, and the West Virginia Chamber of Commerce.

Sen. Shelley Moore-Capito, R-W.Va., declined to endorse a candidate.

Sen. Shelley Moore Capito

Sen. Shelley Moore Capito during a Senate Environment and Public Works Committee markup on May 26, 2021. (Caroline Brehman/CQ-Roll Call, Inc via Getty Images)

CNN chief congressional correspondent Manu Raju tweeted that analysts consider Mooney a possible challenger to Manchin in the 2024 Senate race.

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Last Month, Manchin suggested he would be open to supporting another version of Build Back Better if it were narrowly tailored to combating climate change, lowering prescription drug prices, and reducing the deficit.