Not sure why Trump is considered to be in the same camp as Cruz and Carson, Trump is basically a fatcat amoral land developer with a history of supporting democratic candidates and policies masquerading as a transformative conservative with no previous history of conservativism, his moderate establishment hype based support as well as his pitchfork crazy let's blow shit up support are both vulnerable to be cannibalized from both sides.
It's more about the anti-establishment (anyone but Rubio) voter bloc that exists in the party and how they stack up at this point. That fight, whether that'll be with Cruz or Trump v. Rubio, is one that you'd think the establishment guy would win, but I'm not so sure. You can say that Rubio is gonna be another Romney, but if Romney didn't have the money to sink into his own campaign last time he would've been in more trouble against Santorum/Newt who had no money put together. I don't think Rubio has that same advantage, even if the money will be behind him.
Someone like Trump won't have that problem (if he's in it for the long haul, which is debatable now that he's lost) and Cruz will have a lot of anti-establishment support behind him too and will probably win a shitload of southern states (you know, where the actual base of the party resides).
It's gonna be fascinating to see play out. Because a lot of conservatives really hate Rubio.