I agree.
I love Thompson's political views, but his appearance recently is that of an old, tired, and not entirely healthy man. In order to win over converts to your cause and gain respect from your opponents, a person must radiate an aura of vitality and self assuredness. IMO, this is one of the reasons Bush is so disliked. His inability to communicate effectively and the often commical expressions on his face keep people from being swayed by his arguments or from taking him seriously.
I only wish that Bill Frist had decided to run. He's smart, good looking (without being plastic), and has the charisma to sway people to his point of view. The fact that he isn't a lawyer is also a big plus.