Can the president switch parties in office?

Answer 1

Theoretically, yes. But as a practical matter, it wouldn't be advisable. Look at what happens when a U.S. Senator or member of the House changes parties. Typically, most, if not all, of their staff (who are political operatives) resign en masse, donors demand refunds, etc. Now imagine something like that happening at the presidential level, where there are thousands of political appointees, from cabinet secretaries to deputy special assistants. It would be a nightmare.