A former Republican lieutenant governor of Georgia blasted ex-President Donald Trump as a "fake Republican" during a fiery TV appearance in which he said he'll be switching sides to vote for President Joe Biden.

Geoff Duncan, who served as Gov. Brian Kemp's No. 2 from 2019 to 2023, told CNN on Monday night that "sometimes, the best way to learn your lesson is to get beat and Donald Trump needs to get beat."

Duncan's appearance on "Laura Coates Live" came after he wrote an op-ed for the Atlanta Journal-Constitution titled, "Why I'm voting for Biden and other Republicans should, too."

"This guy's a fake Republican," he said during the interview. "We have to move on as Republicans — we have to — and this is our first step to do it."

Duncan said that although he disagreed "wholeheartedly" with some of Biden's policies, "to think Donald Trump's wholeheartedly a conservative is just fake news at its finest."

Duncan accused Trump of incurring "$8 trillion worth of debt during his presidency" and said Trump failed to deliver after he "told us he was going to build a wall" on the Mexican border.

"It's time to turn the page as Republicans and move on," he said.

His successor, Lt. Gov. Burt Jones, responded by telling the AJC, "Every village has a useful idiot."

"I guess the Democrat party has found theirs," Jones said.

Duncan's endorsement of Biden sparked speculation he was trying to mirror former Democratic Georgia Gov. Zell Miller, who delivered the keynote speech in support of then-President George W. Bush at the 2004 Republican National Convention, the AJC said.