Over the next few days at the Democratic National Convention, Vice President Kamala Harris will accept her party’s nomination and reintroduce herself to American voters. Astead W. Herndon, a national politics reporter and the host of the politics podcast “The Run-Up,” talks through key periods in Ms. Harris’s life that explain what she believes and the kind of president she might become. Guest: Astead W. Herndon, a national politics reporter and the host of the politics podcast “The Run-Up” for The New York Times.