You can say this for the presidency of Donald J Trump: It has familiarised Americans with a number of heretofore obscure facets of their country’s governmental system. The emoluments clause, the 25th Amendment, the Foreign Intelligence Surveillance Court — once upon a time, discussions of the dangers of a president taking money from a foreign state or the prospect of his cabinet removing him from office were the stuff of fiction; the ins and outs of how to get a wiretap on an American citizen were confined to law review articles. Today, they’re the subject of front-page newspaper articles and