Sure he can. A Cruz supporter would probably say neither of them can, but that's why I said I can at least understand them. But if you're going to argue that Rubio is disqualified because of his prior stance, then Trump should be disqualified for the same reason. So which is it? Either, or both?
And moving on from there, the thing for me is that Rubio is a good conservative on issues other than immigration (just put a deep dagger into Obamacare), and Trump isn't.
Oh, Bruce, you are such a tool. Look where Rubio gets his funding - Goldman Sacs (who by the way, also supports Cruz), The Koch Brothers, Sheldon Adelson, etc. But, carry on with your foolishness and Rubio, if nominated, will take a dive so Hillary can win. Mark my words and do your vetting.