That brings up an interesting point. It's not hard to be automatically disqualified from receiving a security clearance - getting a DUI, petitioning to be a conscientious objector, or even a moving violation involving fines over $200 are all disqualifying. However, none of those things prevent you from being elected President. If a convicted felon were elected President, would they actually try to keep him or her from accessing secure information? I wouldn't think so, but I guess it's never been tested either.