Rep. Adam B. Schiff, who is leading House Democrats’ inquisition into Trump-Russia collusion, has not given up on proving that his party’s financed, Kremlin-sourced dossier is true. The Californian pressed his case again this month during a long closed hearing with former Trump campaign volunteer Carter Page to try to revive what had become dormant charges of criminal conduct. Mr. Schiff, who on Wednesday labeled President Trump “the worst president in modern history,” previously said that one of his main objectives for the House Permanent Select Committee on Intelligence investigation is to find which dossier parts are true. In the...