Many vulnerable Democrats have skipped the convention in Chicago -- but not Marcy Kaptur.

The Ohio Democrat, the longest-serving woman in congressional history, now represents a much redder seat after redistricting.

A spokesperson said she traveled to Chicago today to hear Walz -- her former House colleague -- in person after calling for Harris to choose a running mate from the heartland.

Her presence underscores how the new Harris ticket has reenergized Democrats and given even threatened members of the party hope that they can defend their seats in November and retake the House of Representatives.

They see Walz as one of their own: While he served in Congress, he was one of the few House Democrats to win reelection in a district that supported Donald Trump. (Democrats lost the seat when he ran for governor in 2018.)

-ABC News' Rachel Scott and Benjamin Siegel

Kim is the third Democratic Senate candidate to address the DNC, after Angela Alsobrooks and Lisa Blunt Rochester. All three are running in safely Democratic states. By contrast, vulnerable Democratic senators like Tammy Baldwin of Wisconsin and Jacky Rosen of Nevada are staying away.

—538’s Nathaniel Rakich

Stevie Wonder performed "Higher Ground" for the DNC crowd.

"This year I prayed very hard for peace to come to our world's nations, but also to each one of our hearts," he said in remarks before his performance.

"Even though our hearts have been beaten and broken beyond prayer, I know the important action and now is the time to understand where we are and what it will take to win. Win the broken hearts. Win the disenchanted," he said. "Now is the time."

New Jersey Rep. Andy Kim, who just spoke, was captured in a viral photo kneeling to clean up litter-lined floors of the U.S. Capitol after the insurrection.

"What I learned on January 6 is that all of us, all of our, are caretakers for our great republic," Kim told the crowd.