Is Mike Pence Loyal? Trump Is Asking, Despite His Recent Endorsement - The New York Times

President Trump has repeated the question so many times that he has alarmed some of his advisers. But Mr. Trump has not openly suggested dropping Mr. Pence from the ticket in 2020. ....
https://www.nytimes.com/2018/11/16/us/politics/mike-pence-trump-administration.html