How do you know? If there is any foul play Trump will go third party and the GOPe will lose for sure in November.
http://www.realclearpolitics.com/epolls/2016/president/2016_presidential_race.html
Oh, I know, I know... "but the election is 9 months away!!!"
But here's the point - this is the evidence we have NOW. Trump will lose, based on his unfavorables.
So there is two pieces of evidence that he'll lose in the general and Cruz would do better. Can you provide any evidence beyond primary plurality voting (which means *nothing* in the general) that would indicate otherwise?