In Columbia, S.C., on Saturday, a young protester told a reporter that she just didn’t think voting is “how change happens.” “They’ve been telling us to do that for so long,” she added, “and we’ve done it — and look at everything that’s still going on.” Fury over the cruel death of George Floyd, a black man in police custody, combined with fear of a deadly virus and its painful economic impact, make this a dark, dizzying moment in our national life. But African-Americans shouldn’t feel hopeless, because the black vote does matter — it has never mattered more. It...