Tracy Nailor, a 56-year-old Atlanta pediatrician, wasn’t particularly impressed with Kamala Harris when she first ran for president. “I think I succumbed to the narrative about her,” she said. She thought Harris wasn’t experienced or accomplished enough to merit the Democratic nomination. “I just didn’t know enough,” she said. “I didn’t do my homework.” Instead of Harris, she supported the trusted, familiar Joe Biden in the last election.But as Biden’s most recent presidential campaign ground on, her faith wavered. She knew it was going to be hard for the aging president to win again. “I was not hopeless, but I...