Whether Special Counsel John Durham’s inquiry ends with a bang or a whimper will depend, it appears, on how the upcoming trial goes for a man accused of lying to the FBI. If that sounds anticlimactic, it’s because Mr. Durham’s previous attempt to try someone for deceiving G-men fizzled when a Clinton campaign lawyer, Michael Sussman, was acquitted. Yet the real target of this upcoming trial could prove to be the FBI itself.