Sitting on a panel here at Essence Fest, an annual gathering of Black leaders, Rep. Maxine Waters (D-Calif.) brought the crowd alive here Saturday with a declaration: “It ain’t going to be no other Democratic candidate — it’s going to be Biden.” More significant may have been the private forum Waters used to defend the president a day earlier. On a conference call Friday with other members of the Congressional Black Caucus, the 85-year-old House veteran urged the lawmakers to stand with Joe...