Kamala Harris and ‘Coach Walz’ Ease Into Their New Partnership

“Wow,” Tim Walz kept saying, his face spread in amazement. “Wow.”

On Tuesday night, Mr. Walz, the Democratic governor of Minnesota — a scarcely known political figure just two weeks ago — made his giddy, fiery, fidgety, folksy national debut as Vice President Kamala Harris’s running mate.

He waved, with big flapping hands, at the ecstatic crowd. He bowed. He bowed again. He stood behind Ms. Harris as she launched into her fledgling presidential stump speech. He bobbed and grinned. He played with his ear and twiddled his thumbs. And when she ceded the podium to him, 30 minutes later, he played the role of a forceful surrogate.

Ms. Harris, more accustomed to the political choreography of waiting for someone else to finish talking, smiled, her hands clasped. “That’s right,” she said repeatedly. “That’s right.”

The running-mate dynamic can be complicated, even just in terms of staging — how to stand, where to look, what to do with one’s hands.

On Tuesday, though, both Mr. Walz and Ms. Harris seemed comfortable in their new roles. He gushed over her “joy.” The whole night, he looked like a guy who had won the political lottery and could not believe his luck.

She seemed very excited about football.

“Coach Walz,” as Mr. Walz was once known — back when he was a high school social studies teacher and football coach — had helped lead his team to a state championship. He was also the faculty adviser for the student gay-straight alliance.