If you want me to address your post, it implies pretty much the same mistaken notion about what a comeback is. You have to have been somewhere to come back is I think how you put it. He is somewhere, he is in the race, far at the back of the pack, ahead of Pataki but behind Rubio and hanging out with Fiorina and Christie, which is exactly where a comeback comes from. What you said makes no sense in English terms. He could technically make a comeback (although no one thinks he will). If you know what a comeback is, then you know that's what Bush has to have if he wants to win. But you said Bush can't make a comeback because he never was "somewhere".
So, in the famous words of Inigo Montoya,
I think we both agree that Bush will not make a comeback, so we have that going for us.