Bush has done an excellent job of portraying that image. I don't think he's an idiot at all, and I think his public image is a calculated one designed to make him more appealing to the average Joe. It has obviously worked.
I agree 110% regarding the 'image' argument.
After all, he is a multimillionaire who went to Yale, owned a baseball team, and spent many years in and around Washington growing up.
Somehow, he was able to sell himself (twice!) as being a folksy outsider who is just a common guy like you or me.
That's an incredible accomplishment.