He also targets President Joe Biden's failed $1.75 trillion Build Back Better plan, which Manchin himself killed when declaring his opposition to it late last year.
Mooney and McKinley are battling against the GOP nomination to represent West Virginia's 2nd Congressional District after the state lost a seat to redistricting after the 2020 census.
It's rare for sitting lawmakers to wade into a race pitting two incumbents against one another in a primary. However, it is even rarer to do so for the opposing party.
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Manchin is the only Democrat currently representing deep-red West Virginia in Congress. Trump defeated the state by roughly 40 points in the 2020 presidential election.
"I've always said if I can't go home to explain it, I can't vote for it. And that's why I opposed Build Back Better," the senator said in the TV spot.
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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."
Manchin's fellow West Virginia senator, Republican Shelley Moore Capito, has not praised anyone in the race.
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McKinley was one of 35 House Republicans to vote in favor of a bipartisan commission to examine the January 6 Capitol riot. However, he's since opposed the House Select Committee assembled by House Speaker Nancy Pelosi.
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He also opted for Biden's $1.2 trillion bipartisan infrastructure deal, which both Trump and Mooney have condemned him for.
"Congressman Alex Mooney is a conservative warrior running in West Virginia’s 2nd Congressional District," the ex-president said in a statement last week.
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He slammed McKinley, declaring Mooney's "opponent is a RINO who supported the 'Infrastructure Bill' and the Sham January 6 Unselect Committee."
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"Alex fights for our Veterans, for Energy and Clean Coal, Election Integrity, our Borders, Jobs, and against the horrible drug epidemic. On May 10th, Vote for Alex Mooney, who has my Complete and Total Endorsement. I love West Virginia!"
Trump-backed Mooney has out-raised McKinley by more than $3 million in this campaign cycle, according to the most recent filings through April 20.
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According to a poll by the Morning Consultant, Manchin now has an approval rating in West Virginia of 57%, which is one of the top 10 highest approval ratings among all senators. That has increased from only 40% in the first quarter of 2021.
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