and what would happen if he/she couldn’t qualify for one?
I am pretty sure we have done this before. Presidents have access to most things a clearance allows someone to see by default. It is part of the job description of being President. The same would be true for Cabinet members as well for the things their job requires them to know.
Assuming that Bush was a normal guy applying for a lower-level job requiring a high-level clearance, he might have some problems because of the drinking and alleged drug abuse. Clinton might have problems too if he was some regular guy and I am sure many past presidents would.
I didn’t search through the archives before asking this, althought I don’t recall seeing anything about it. It was just one of those questions that pop into mind. I wasn’t inquiring as to specific presidents, just asking as a general question.
Here is the similar thread I was thinking of:
http://boards.straightdope.com/sdmb/showthread.php?t=235126&highlight=clearance