Tim Walz, now running for vice-president, took the stage Wednesday night in a way that felt more like a pep rally than a political event. Before he spoke, about a dozen players from the high school football team he coached to a Minnesota state championship years ago ran onto the stage, some sporting their old jerseys, as a marching band played loudly.

When Mr. Walz finally appeared, the crowd in the packed arena waved signs reading “Coach Walz” and chanted “coach, coach, coach!” This was his first major opportunity to introduce himself to the nation, so his speech focused heavily on his personal journey. He shared stories about his time as a football coach, his upbringing, his enlistment in the Army National Guard, his career as a high school teacher, and his service as a congressman and governor.

In the front row, his daughter Hope, 23, and son Gus, 17, were visibly emotional, with Gus mouthing “That’s my dad!” as the camera zoomed in on him. Mr. Walz’s folksy delivery, which the Democratic campaign hopes will resonate with moderate voters in key Midwestern states, included a rallying cry: “We are not going back,” a clear message aimed at Donald Trump and his running mate, JD Vance.

His speech followed a variety of speakers and entertainers on the third night of the Democratic National Convention in Chicago, where Oprah Winfrey made a surprise appearance, earning the most enthusiastic response of the evening.

The four-day event will conclude Thursday night when Vice-President Kamala Harris formally accepts the Democratic nomination, just over a month after President Joe Biden withdrew from the race. But on Wednesday, the spotlight was on Tim Walz, a man who was relatively unknown to most Americans until recently. He echoed themes from his earlier speech in Philadelphia, saying, “In Minnesota, we respect our neighbors and the personal choices they make. And even if we wouldn’t make the same choices for ourselves, we’ve got a Golden Rule—mind your own damn business!”