Former Rep. Adam Kinzinger said he never thought he'd be at the DNC -- but the Republican went on to explain what drew him to support Harris.

"Donald Trump has suffocated the soul of the Republican Party," he said. "His fundamental weakness has coursed through my party like an illness. Sapping our strength. Softening our spine. Whipping us into a fever that has untethered us from our values."

He said the Democrats are "as patriotic as" Republicans, continuing a theme of the night, as the crowd chanted "U.S.A.!"

After recounting the "profound sorrow" of Jan. 6, he said he suspected other conservatives would belong at the DNC as well.

"Democracy knows no party. It is a living, breathing ideal that defines us as a nation. It is the bedrock that separates us from tyranny -- and when that foundation is fractured, we must stand united to strengthen it," he said, while urging people to "vote for our bedrock values" by voting for Harris.

Actress Eva Longoria hyped up the crowd by taking the Latino motto "Si, se puede," "Yes, we can," which was used throughout Barack Obama's campaign, and adding a twist.

"Tonight, I'm here to tell you, yes, she can. So, we're going to say, 'she se puede,'" she said leading to a chant from the crowd.

Our colleague at 538, Mary Radcliffe, did a deep dive earlier this week into polling crosstabs to see how Harris is doing with the coalition of voters that successfully elected Biden in 2020. We're hearing from Black, Latino and Midwest politicians and celebrities tonight because that's part of who Harris has to get to the polls to recreate that winning formula this November. You can read more detail in our story.

— 538's Monica Potts

Former Rep. Adam Kinzinger is delivering a prime-time speech in support of Harris -- rounding out a slate of Republicans who have spoken at the DNC this week, including former Georgia Lt. Gov. Geoff Duncan, Mayor John Giles of Mesa, Arizona, former Trump White House national security official Olivia Troye and former Trump White House press secretary Stephanie Grisham.

Kinzinger, who retired from the House in 2023, has been a vocal Trump critic over the years, and although he describes himself as a "proud conservative," he endorsed then-candidate Joe Biden for reelection in June.

The former Illinois congressman sat on the House's Jan. 6 select committee that investigated the attack. He was also one of the 10 House Republicans who voted to impeach Trump on a charge of inciting the Jan. 6 attack.

Since Harris replaced Biden as the Democratic nominee, Kinzinger has supported the vice president, saying she stands for democracy.

-ABC News' Sarah Beth Hensley