Who is Controlling what Bush Says and Thinks?

Derek wants to know what it is that's being said over Bush's earpiece -- assuming it is, as many have sworn, a speaker so that a remote person can talk to him.

Forget what's being said -- I want to know *who* it is that control what Bush says in public. Is it Karl Rove? Is it Dick Cheney? Who feeds Bush the answers that he cannot produce on his own?