Trump's job is to clear a path for Rubio by sucking votes from Cruz. Just like Santorium sucking votes from Newt in 2012 cleared a path for Romney.
See that works both ways. Cruz and Trump better learn how to keep Rubio down or they both will lose.
Well I would cede your point had Cruz brought the issue to this campaign that Trump did. Cruz spent months as Trump “me too” candidate. So since Cruz is campaigning on Trump issues then I can say that it is Cruz that is sucking up votes that should go to Trump. Not vice versa.