Ever since President Trump started playing armchair museum curator last year, the White House has employed a number of strategies to try to influence exhibitions at the Smithsonian. It has sent threatening letters, published a memo that reads like an exhibit hit list, and even resorted to an occasional bit of online trolling.The Smithsonian has certainly undergone a small number of changes as a result of the pressure, but compared with, say, the Kennedy Center and the National Endowment for the Humanities, it has shown that it is not so easily breached. Yesterday, however, House Republicans appeared poised to push...