The question of whether a President can pardon himself is an open one subject to plenty of thoughtful commentary, most notably by my friend Brian Kalt. In some unrelated research that I was doing this weekend, I came across a speech that President Truman gave at the West Point Commencement in 1950.
“As President of the United States, under the Constitution, the President has power to pardon anybody for anything but impeachment. Of course, he couldn’t pardon himself.”
This was kind of a throwaway line, but I don’t think that any other President (save perhaps for Trump) ever discussed this issue publicly.