Tinhorn
Main Entry: tin·horn
Pronunciation: 'tin-"horn
Function: noun
Date: 1885
: one (as a gambler) who pretends to have money, ability, or influence
As you can plainly see Bush is not a tinhorn since he pretends to none of this. He has and has had all of it for a long time.
Oh, one other lesser known definition of tinhorn is someone that spells ASS, ARSE.