Put aside Russian collusion for a moment. Press pause on possible presidential obstruction of justice. Forget Stormy Daniels. The most significant recent development involving the president may be that the special counsel, Robert Mueller, has subpoenaed Trump Organization business records as part of his inquiry into Russian interference in the presidential election. Those documents — and records recently seized by the F.B.I. from the president’s personal lawyer Michael Cohen — might answer a question raised by the president’s critics: Have certain real estate investors used Trump-branded properties to launder the proceeds of criminal activity around the world? We pored over...