A Romney v Barry S. race is the only one that opens up the slim possibility of a 3rd party Ventura/Perot style run. It is the only combination that allows an opening IMO.
To paraphase Judge Napolitano:
The law of the land is that when the government cease to recognize guaranteed natural rights it is the duty, underscore duty of the people to alter or abolish it.
How do you alter or abolish it when you have a choice between Mitt and ‘Zero’?
http://www.youtube.com/watch?v=9b3Q89FZoY0