Except when Obama came along. Dr. Carson is an unusual scenario because he's not a politician and he's well respected. He will be unbeatable if he chooses to run.
I'd love to watch a republican primary consisting of Ted Cruz, Rand Paul, Marco Rubio, Paul Ryan, and Ben Carson. I'm sure they will try to greatly decrease the amount of debates from last year though which will decrease the entertainment.
Ted Cruz is speaking today at cpac btw.