Cruz is impressively stupid. I’m pretty sure he had well over 50% support on FR at one point (the 1/20 results, the earliest I could find, had him at 46%, a respectable showing), then he decided to backstab conservatives in favor of the GOP-e. Now his political career is going down in flames along with the careers of his newfound GOP-e buddies.
Candidates and their teams may one day study the 2016 Cruz campaign in order to learn what NOT to do, if you intend to win.