Graham could have some sort of top-secret South Carolina GOTV plan that propels him to a respectable finish in the Palmetto State. Finishing in the top 3 would be seen by the media as some sort of miracle, and they'd probably through him around as a "potential nominee" or "rising star" for a week or two after that. For that reason alone, I think Graham should top this list - all of the other candidates just don't have a viable path, Graham has a highly unlikely yet possible path.
It wouldn't be a miracle because South Carolina is his home state.