Just for kicks, I’ve taken the Real Clear Politics chart of the Republican race and done two things with it. First, I eliminated all candidates but Rick Perry and Herman Cain. Second, I shifted Herman Cain back about 45 days, and up about 5 points.
Red is Cain. Blue is Perry. The shapes of the peaks look pretty similar to me.
To my biased eye, this just supports my theory that ridiculously high net favorability ratings just don’t last. Watch Newt Gingrich. I expect him to follow the same path.