Good article at the Conservative Review, “Why the Establishment Fears Cruz More Than Trump.”
This sums it up:
“…Trump is a dealmaker running a campaign as a disrupter to the status quo. Cruz is a proven disrupter to the status quo. That is a very big difference indeed. The political industrial complex believes deep down that they can negotiate with the author of The Art of the Deal
; they know they will lose the levers of power with Ted Cruz. You can see it in the voracity and frequency of their attacks. The establishment consultants and chattering class know they have the most to lose with a Cruz presidency. What do they lose with a Cruz presidency? The very levers of power by which they enrich themselves: the Republican Party apparatus …”