Julian Castro, a rising star in the Democratic Party, was stumping for Hillary Clinton in southeastern Iowa on Sunday when a union leader extended a hand and a question in Spanish.
“I heard Clinton might pick you for vice president,” said Jose Pulido, who represents workers at a hog slaughterhouse that has helped draw thousands of Latinos to this small city straddling the icy Des Moines River.
Castro flashed a toothy smile. “Quién sabe,” he answered, shaking his head. Who knows?
As the secretary of Housing and Urban...