I have thought for a week that Trump, barring a total catastrophe, has this locked up. What I think you're seeing with Carson is a natural ebb and flow that usually happens with the #1 candidate. First it was Walker, then it was Rubio, then it is Carson, probably next week or two it will be Fiorina. Cruz seems pretty well stuck at 6-8%. They get knocked down after they get thrust into more limelight.
He's a wonderful man, but I don't want him as president. Surgeon General, even veep to learn a little about politics. I don't think he's cutthroat enough to be president (no pun intended).