They can demand all they want, but they are the desperate ones right now, not him.
He has more delegates going to the convention that all candidates besides Trump combined. If there is anyone more powerful than a King, it’s a kingmaker, and I think Cruz would not hesitate to give the crown to Trump made from the gold the establishment gave him.
It would truly gripe me if Cruz had 600-800 and Trump had 1175, and Cruz went for the blackmail to get on the ticket.