CHICAGO — Geoff Duncan was never expected to win a Georgia House seat, let alone rise to the state’s No. 2 post. But that’s nothing compared with his path to becoming one of the nation’s most prominent “Never Trumper” voices.

Over the past decade, the Republican’s surprising arc put him at odds with his onetime allies. His former top aide calls him a publicity hound. His GOP successor in the lieutenant governor’s office mocks him relentlessly. The state party wants to exile him.

But Duncan has ignored the backlash in his transformation from a Donald Trump supporter to lukewarm critic to opponent so fierce he was invited to fill a coveted speaking spot at the Democratic National Convention.

His speech Wednesday might be the biggest moment yet in Duncan’s political career, joining just a handful of current or former elected Republican officials who have vouched for the Democratic nominee under the biggest spotlight in American politics.

His is not exactly a Zell Miller moment. The two-term Democratic Georgia governor was a U.S. senator when he delivered a keynote speech in 2004 on behalf of Republican President George W. Bush. Former President Jimmy Carter, a Democrat, called it “historically unprecedented disloyalty.”

As a U.S. senator and former Democratic governor, Zell Miller gave the keynote speech at the Republican National Convention in 2004 to show his support for Republican President George W. Bush. Former Democratic President Jimmy Carter called the act “historically unprecedented disloyalty.” File

Credit: Photo by Stephen Morton/Getty Images

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Credit: Photo by Stephen Morton/Getty Images

Duncan, by contrast, is a one-term lieutenant governor who has hardly shocked partisans with his endorsement. But with few high-ranking Republicans willing to oppose Trump’s comeback, Duncan has filled a vacuum.

Echoing his message for months, Duncan said Wednesday that his endorsement of Vice President Kamala Harris is no treachery of GOP values. It’s Trump, he said, who has abandoned the party.

“If you vote for Kamala Harris, you’re not a Democrat,” he said to an ear-splitting ovation from thousands crammed into the United Center. “You’re a patriot.”

He and other Republicans vouching for Harris could play a decisive role. Harris’ campaign hopes they can help her sway mainstream Republicans and independent voters on the fence in November — the same bloc that helped swing close elections in Georgia the past three cycles.

To some Republicans who know him well, Duncan is a misguided attention-seeker who bashes Trump to help land contracts with CNN and The Atlanta Journal-Constitution, where he serves as a contributor.

Chip Lake, a former Duncan aide who left the job after a bitter falling out, said his ex-boss has an “insatiable thirst” for the spotlight that clouds his judgment.

Lake predicted that Duncan will wake up after the election and, regardless of who wins, “find that his former party doesn’t want him back and his current party and cable news client have exhausted their use for him.”

Then Lt. Gov. Geoff Duncan, a former pitcher at Georgia Tech, throws a baseball to another Georgia Tech pitcher, Hugh Chapman, on the last day of the legislative session in June 2020. (Hyosub Shin / Hyosub.Shin@ajc.com)

Credit: HYOSUB SHIN / AJC

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Credit: HYOSUB SHIN / AJC

To his admirers, Duncan is a truth-teller, a rare statewide Republican official willing to oppose the former president, though safely outside the confines of elected office.

“He’s very bold,” said Democratic strategist Tharon Johnson, who added that Duncan could have easily “fallen back” after President Joe Biden dropped out of the race. “He’s done the exact opposite. He’s doubled down on his support.”

A close call

A health care executive from Atlanta’s northern exurbs, Duncan in 2011 ran for a newly created Georgia House district that local activists believed was drawn to favor former state Rep. Tom Knox’s comeback bid.

Duncan won the seat in 2012 by 55 votes after an outreach strategy that stunned local party leaders confident that Knox would prevail.

Never content to be a backbencher, Duncan led the push for legislation creating a special tax credit for donating money to a local hospital. Eyeing an open lieutenant governor’s race, he prepared for his run almost two years before the 2018 election.

He was the heavy underdog against 16-year state Sen. David Shafer, who had accumulated a long list of IOUs as one of the chamber’s most powerful Republicans.

But Duncan hit Shafer hard on the campaign trail, questioning his financial record and reminding voters that his GOP opponent was accused, and later cleared, of sexually harassing a lobbyist. He was aided, too, by more than $3 million in spending from a Washington-based outside group.

After eking out a narrow runoff victory, Duncan swept past a Democrat that November and took office with Trump’s endorsement.

Lt. Gov. Geoff Duncan, right, was a loyal ally to both Gov. Brian Kemp, left, and President Donald Trump during his early years in office. But that changed after the 2020 election, when Trump-promoted election fraud lies led to threats against Duncan and his family. (Arvin Temkar / arvin.temkar@ajc.com)

Credit: arvin.temkar@ajc.com

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Credit: arvin.temkar@ajc.com

In his first years in office, Duncan was a loyal ally to both Gov. Brian Kemp and Trump. But that changed after the 2020 election, when Trump-promoted election fraud lies led to threats against Duncan and his family.

At first, he echoed Kemp by mildly rebuking Trump and urged fellow Republicans to focus on the future. But he ultimately broke with Kemp by forcefully condemning Trump and his MAGA backers.

Duncan published a book, “GOP 2.0,” outlining his vision of a post-Trump party. He called proposed rollbacks to voting rights “solutions in search of a problem.” He boycotted a Senate vote on election restrictions.

And in 2022, shortly after he decided against seeking a second term, he refused to back two Trump picks for statewide office: U.S. Senate nominee Herschel Walker and Burt Jones, the candidate to succeed Duncan. Jones, who prevailed, hasn’t forgotten the insult.

In a fundraising email to supporters this week, Jones called his predecessor a “disgrace to Georgia.”

“Geoff is the Democrats’ useful idiot,” Jones added, “being manipulated to deceive our voters.”

Under its chair, Josh McKoon, the Georgia GOP recently moved to formally brand former Lt. Gov. Geoff Duncan a traitor to the party, block him from qualifying to run on the GOP ticket and label him a “trespasser” should he ever attend another event. McKoon wrote to Duncan, saying, “You are not and never will be considered a Republican ever again.”

Credit: Seeger Gray/AJC

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Credit: Seeger Gray/AJC

The Georgia GOP, once led by Duncan’s old adversary Shafer, went a step further. Party leaders recently moved to formally brand him a traitor to the party, block him from qualifying to run on the GOP ticket and label him a “trespasser” should he ever attend another event.

“You are not and never will be considered a Republican ever again,” party Chair Josh McKoon, a close Shafer ally, wrote to Duncan. “I request that you govern yourself accordingly.”

Duncan has shrugged off the backlash. In a recent interview on the “Politically Georgia” podcast, he offered a dollop of advice to other Republicans worried about Trump’s influence.

“Do the right thing. Listen to that tiny little voice in your head that tells you Donald Trump is the worst thing that not only happened to the party but this country,” Duncan said.

“This is a temporary moment of insanity for the Republican Party,” he added, “and the only way to fix it is to get rid of him.”

Video reporter Eli Goodstein contributed to this article.