West Virginia Democratic Sen. Joe Manchin III has been an honest broker in his negotiations with both the Biden and Trump administrations, while in "Build Back Better" negotiations as of late, his party leadership "overplayed its hand" and lost the Mountaineer's support, House Minority Leader Kevin McCarthy said Monday.

McCarthy, R-Calif., told "Fox News Primetime" that "Democrats made a fatal mistake" in passing the far-left socioeconomic overhaul through the House without having conferenced or passed through the Senate, suggesting the moderate Manchin did not have any opposite numbers in the lower chamber for the liberal leadership to be as concerned about.

"It was surprising but if you listen to Joe Manchin, one thing about him, he has been exactly and consistently honest all the way through: He said he would and even signed an agreement he would not go higher than the $1.8 trillion," he said.

"And now [The House] has voted for 87,000 IRS agents to spy on you – They voted to open the border and make people legal citizens when they came here illegally. They voted to take away work requirements [for handouts]. This is a very bad vote. But Joe Manchin kept his word. Now, I didn’t think it would happen," McCarthy continued.

"I thought the odds were that they [Democrats] would get something through. This is a real defeat all around, and they overplayed their hand."

SCHUMER HITS MANCHIN FOR FAILING TO SUPPORT BUILD BACK BETTER, MAINTAINS DEMOCRATS WILL ‘FIND A WAY FORWARD’

McCarthy also reacted to the ongoing intraparty blowback toward Manchin, the sources of which have included White House Press Secretary Jennifer Psaki, Reps. Ilhan Omar of Minnesota and Alexandria Ocasio-Cortez of New York, and Sen. Bernie Sanders of Vermont.

"[F]or those who thought they would intimidate Joe Manchin in West Virginia, they ought to look again. Joe Manchin is more popular in West Virginia today because of what he said yesterday. And they are not going to intimidate him. More people will stand with him in West Virginia," McCarthy predicted.

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U.S. Senator Joe Manchin (D-WV) talks to reporters on Capitol Hill in Washington, U.S., January 19, 2018. REUTERS/Yuri Gripas

McCarthy added that Manchin is only the latest Democrat to buck his party in a major way, pointing to how New Jersey Rep. Jeff Van Drew switched his affiliation to Republican during the Trump years.

"We had an individual reregister from Democrat to Republican and I think there are a few other Democrats out there that are thinking about it," he said.

"Why? Not because they changed, but the party has changed. The Democrat Party is no longer the Democrat Party of old. This is a socialist Democrat party. Bernie Sanders says it; AOC and others. And that is out of step with the mainstream of America."

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"That is their problem. They are letting that wing of the socialist wing of the party dictate their policy; dictate the intimidation," McCarthy added. "Lucky for us, Joe Manchin stood up to it."