In 2000, the Bush campaign made a big deal about answering-without-answering questions about Bush's past cocaine usage by having him say that he could have passed the WH background check during his father's administration. This would have meant, according to his assertion about what that background check entailed, that he hadn't done cocaine since 1978, though he strangely stated that it meant that he hadn't done anything bad since 1974. All these inconsistencies served to deflect the press from the real issue, while they were chasing around trying to parse what the hell was being claimed. See Bushwatch for full details.
From what I understand, what we'll be hearing soon is not only would Bush not have passed the WH background check at the time -- he also wouldn't have been in compliance with federal drug laws at the time.
As they say, developing...