One of the key things to think about when handicapping a presidential nomination battle is not just who is ahead at the moment, but who is most likely to benefit once the field inevitably narrows down and key Republicans begin making endorsements. On that score, Texas Gov. Rick Perry would seem to be a huge threat to Mitt Romney.

If Rep. Michele Bachmann, R-Minn., is forced to drop out at one point in the race, it seems clear that Perry would be in the better position to pick up support among her Tea Party/social conservative constituency than Romney. You can make arguments both ways for where Herman Cain and Rick Santorum (both of whom endorsed Romney in 2008) supporters may go. But none of those candidates, or Newt Gingrich or Jon Huntsman, have deep enough support to make a huge difference when exiting the race. That moves us to the current non-candidates.