Why are Democrats protecting the Beltway smear-specialist firm Fusion GPS? Specifically, why are the party’s senators supporting Fusion chief Glenn Simpson in his refusal to say who paid to get that infamous President Trump-smearing “Russian dossier” drawn up? As The Wall Street Journal’s Kimberly A. Strassel notes, Dem senators even passed on the chance to publicly question Jared Kushner and former Trump campaign manager Paul Manafort, rather than also expose Simpson to public questioning. Maybe Democrats simply didn’t want anything to mess up their “collusion” narrative. Or perhaps they fear their own party used Fusion to commission the hit. She’s...