In his recent testimony to Congress, Deputy Attorney General Rod Rosenstein undoubtedly intended to sound reassuring. “I am quite confident,” he proclaimed, “about my conduct throughout this investigation.” Rosenstein may have reason to feel confident. He’s in a difficult position and his conduct may indeed be above board. And, under normal circumstances, Congress and the public might be comforted by his guarantee. But that’s the rub: These circumstances are far from normal. We’re in the midst of one of the most important scandals in memory: Our intel agencies and some public officials within them are suspected of abusing power and...