Let’s see. The Clinton campaign hires Fusion GPS, an opposition research firm, to investigate the Trump campaign. Fusion hires a former British spy, Christopher Steele, who produces a dossier based on Russian sources full of rumor, hearsay and an occasional fact to allege collusion between the Kremlin and Trump campaign. The dossier gets to the FBI, which uses it to justify opening a counterintelligence probe of the Trump campaign, perhaps including a judicial warrant to spy on Trump officials. Then Fusion has Mr. Steele privately brief select media reporters, ensuring that the dossier’s contents become public before the...