Cruz is basically the "pure" Republican candidate. He is an incredibly smart, privileged elite who decided to exploit the Tea Party movement to gain power, so it's no wonder that people like Glenn Beck and Erick Erickson support him. He is by far the most disliked Senator in Congress though, which tells you something if not even any Republican colleagues want him to win.
The general wisdom suggests that Cruz getting the nomination would lead to an electoral disaster of Barry Goldwater proportions.
Also it bears mentioning that Cruz just seems like a weird dude:
https://www.youtube.com/watch?v=KqpHTFJO4mE