Anderson Cooper offered Kamala Harris a layup. Instead she laid an egg. “Is there something . . . in the last four years that you think is a mistake that you have learned from?” he asked during Wednesday’s CNN town hall. Ms. Harris responded to this standard job-interview question by offering up a sticky gumbo of an answer that had something to do with raising children and nothing to do with honest reflection. It was bad—not only the wrong answer, but the wrong approach.