Vice President Kamala Harris’s acceptance speech started slow, getting bogged down in a familiar recitation of her biography. But it got stronger over time, really hitting its stride when she got around to a topic that’s often dry: foreign policy. There, she showed a facility with policy and an aptitude for navigating deeply divisive issues like Israel-Palestine that did wonders for her commander-in-chief credibility. Part of what worked was Harris’s palpably emotional delivery. But there...