A few years ago, Sidney Powell, a former federal prosecutor and the author of the book “Licensed to Lie: Exposing Corruption in the Department of Justice,” was probably best known as a critic of the Mueller probe into Russia’s meddling in the 2016 Presidential election. After Michael Flynn, Trump’s former national-security adviser, pleaded guilty to the felony of lying to the F.B.I. in the course of that investigation, she publicly urged him to retract the plea; Flynn fired his lawyers and hired her instead. Donald Trump praised the decision. “General Michael Flynn, the 33 year war hero who has served with distinction, has not retained a good lawyer, he has retained a GREAT LAWYER,” he wrote on Twitter, wishing them both luck. Ultimately, however, Powell’s legal prowess was not required: ...