Well .. we don't know who they used in their poll. These just happen to be those who get the highest "NO" votes that they're willing to talk about.
And .. if Romney and Allen didn't get that many "NO" votes - then there would be plenty of reason not to mention them.
To me it shows who the CNN-types want you to believe is the contender vs who the real contender might be. They love to throw McCain and Rudy and Jeb out there as the front runners, when neither of them have that strong a showing in other polls.
I sure hope we never consider Romney. That would be as bad as Clinton. Amen.