T.Rump and Cruz have it within their power to stop any “parachute” candidate. T.Rump has something like 750 delegates; Cruz 640. Together that is 1,390 delegates.
If T.Rump and Cruz made a deal, with T.Rump as the nominee for President and Cruz for Vice President, the contest would end.
The reality is that T.Rump is an egomaniac who will not make such a deal under any circumstances and will bolt the party.
I’m thinking their meeting last year was about just such a situation.