Well, his indiscretions were public and well-known before he became President and he continued them in the Oval Office! And she’s married to that debauchee. Offhand I seem to recall that if someone is evil or in cherem, halacha essentially carries over his status and/or excommunication to his wife. And she herself strongly supported toeiva marriage (a position I don’t think Trump took) and other overt acts of public policy support for immorality.
And I do think that Trump will be overall bad as President but that Clinton will be worse. It is a very close call though and I could be wrong. (How’s that for humble pie?)