How many polls does the GOP base need to realize that their only winning option is Romney? Or would they prefer to lose the whole election with one of the clown candidates? What is so terrible about Romney that you'd rather keep Obama? Does it hurt your feelings that he won't do the John Wayne cowboy act?
Paul does better with independents in most polls. His numbers are usually lower due to neocons claiming he is an isolationist, a Justin Bieber fan, or something else equally stupid, so their candidate looks good by comparison. These people would vote for Paul in the general. They just don't want to admit it, because he is not their guy/guys.
Romney does better with Republicans, but the ones that don't like him see him as no different than Obama. This includes libertarians/paleocons and so-cons. Why let the Republican party get the blame for the stupid policies? Romney also won't win the increasingly anti-war independents.