The FBI and Special Counsel Robert Mueller repeatedly kept alive a damning narrative that investigators knew to be false: namely, that a junior Trump campaign aide as a favor to the Kremlin had “gutted” an anti-Russia and pro-Ukraine plank in the Republican Party platform at the GOP’s 2016 convention. Federal authorities used this claim to help secure spy warrants on the aide in question, Carter Page, suggesting to the court that he was “an agent of Russia” – even though investigators knew that Page was working for U.S., not Russian, intelligence, and that they had learned from witnesses, emails and...