Harris and Walz make their national entrance before upbeat Democrats

Vice President Kamala Harris, the Democratic presidential nominee, and her running mate, Gov. Tim Walz of Minnesota, take the stage Tuesday at a campaign rally for his introduction at the Liacouras Center in Philadelphia. (Erin Schaff/The New York Times)

PHILADELPHIA — Vice President Kamala Harris finished her two-week sprint to find a running mate by formally introducing Gov. Tim Walz of Minnesota to the Democratic Party and the nation during a jubilant rally on Tuesday evening in Philadelphia.