A presidential pardon is absolute for any any Federal crimes, and the legality of a Federal/presidential pardon for state crimes is an untested area of law, although theoretically, the president can only pardon for federal offenses.
A pardon is so all-encompassing that even if it is proved that the pardon paw the result of a a payment/bribe, it is still totally valid and irrevocable.
Although a president cannot use the pardon power to avoid impeachment, it is felt by many that if the president was charged with a crime in addition to being subject to an impeachment action, he could probably pardon himself for the criminal segment.
I know; it’s not logical. It’s law.
Thanks....very cogent, yet sad....I have thought about the prospect of a president being able to pardon him/herself....it’s an upside down world these days