The infamous anti-Trump dossier, once toasted by the FBI and liberals, has faded from Washington’s political dialogue. The FBI had embraced the opposition research written by former British spy Christopher Steele and funded by the Hillary Clinton campaign and the Democratic National Committee in 2016. Congressional Democrats frequently cited its unverified collusion charges in 2017. Today, Democrats seem to have left the document behind. References to the dossier are nonexistent in “The Threat,” the newly released memoir of former acting FBI Director Andrew McCabe. There is also no mention of dossier writer Mr. Steele or Fusion GPS, the investigative firm...