WASHINGTON — Former Rep. Adam Kinzinger, the Illinois Republican who forcefully repudiated then-President Donald Trump after the Jan. 6 attack on the Capitol, endorsed Democratic President Joe Biden on Wednesday, blasting the presumptive GOP nominee as a “direct threat to every fundamental American value.”

Kinzinger’s endorsement came one day before Biden and Trump square off in Atlanta for their first 2024 presidential debate. And the Biden campaign hopes that the endorsement helps him win over moderate Republicans who feel alienated by Trump.

In a video message, Kinzinger said his life has been guided by the belief that America is a beacon of freedom. “So while I certainly don’t agree with President Biden on everything, and I never thought I’d be endorsing a Democrat for president, I know that he will always protect the very thing that makes America the best country in the world: our democracy,” he said.

“Donald Trump poses a direct threat to every fundamental American value,” Kinzinger continued. “He doesn’t care about our country. He doesn’t care about you. He only cares about himself, and he will hurt anyone or anything in pursuit of power.”

Responding to Kinzinger, Biden said on X: This is what putting your country before your party looks like. I’m grateful for your endorsement, Adam.”

When asked for comment on Kinzinger’s endorsement of Biden, Trump campaign spokesperson Steven Cheung responded, “Who’s Adam Kinzinger? Isn’t he the crybaby?”

After the Capitol riot, Kinzinger was one of 10 House Republicans who voted to impeach Trump for incitement of insurrection — the former president’s second impeachment. He also voted to create the select committee to investigate the Jan. 6, 2021, attack on the Capitol and was subsequently named to serve on the panel by then-Speaker Nancy Pelosi, D-Calif., alongside former Rep. Liz Cheney, R-Wyo., another prominent “Never Trump” conservative.

Kinzinger, an Iraq and Afghanistan war veteran who received death threats for serving on the Jan. 6 panel, did not seek re-election to the House in 2022.

Earlier this year, Trump attacked Kinzinger and Cheney as “two very sick Republicans” and “far worse than any Democrat that ever lived.”

In his video Wednesday, Kinzinger directly invoked Trump’s involvement in Jan. 6, speaking over images of violence at the Capitol that day.

“Trump attacked the foundation of this nation, encouraging a violent mob of his supporters to march on the Capitol to prevent the peaceful transition of power,” Kinzinger said.

“Now, he has become even more dangerous. He’s called for the ‘termination’ of the Constitution. He wants to be a dictator on day one, he actually said that. And he’s continuing to stoke the flames of political violence.”

In closing, the former congressman said, “There is too much at stake to sit on the sidelines.”

“So to every American of every political party and those of none, I say: Now is not the time to watch quietly as Donald Trump threatens the future of America,” Kinzinger said. “Now is the time to unite behind Joe Biden, and show Donald Trump off the stage once and for all.”

Kinzinger is the rare, prominent Republican who has formally endorsed Biden. Other notable Republicans who’ve broken with Trump and have warned about the dangers of a second term have not endorsed the Democratic president. They include Cheney; former Maryland Gov. Larry Hogan, who is running for the Senate this fall; and the pair who ran on the 2012 GOP ticket together, retiring Sen. Mitt Romney, R-Utah, and former Speaker Paul Ryan, R-Wis.

The Biden-Harris campaign said it hopes Kinzinger’s endorsement helps convince anti-Trump Republicans that they “have a home” with Biden. The endorsement came weeks after the Biden campaign named Kinzinger’s former chief of staff, Austin Weatherford, to lead GOP outreach for Biden.

“Congressman Kinzinger represents the countless Americans that Donald Trump’s Republican party have left behind. Those Americans have a home in President Biden’s coalition, and our campaign knows that we need to show up and earn their support,” Biden campaign manager Julie Chavez Rodriguez said in a statement.

“Congressman Kinzinger’s endorsement doesn’t just make our campaign stronger — it will better equip us to win the hearts and minds of the voters committed to fighting for the future of our democracy and stopping Donald Trump.”

This article was originally published on NBCNews.com