People seem to think the GOP establishment has some sort of magical veto power on who gets nominated and who doesn't. We're not in the twenties anymore, that is not how it works. The only thing that the 'establishment' candidate has is better access to the donor class, but people like Cruz and Paul are going to be able to go head to head with people like Christie and Bush when it comes to fundraising even if the latter group has the mystical 'establishment' stamp of approval.
Remember, Romney didn't get nominated because he is the 'establishment choice' or whatever, he won because his competition sucked and he had a lot of money and they didn't.
Yes, but the GOP tends to nominate figures from the "establishment" wing of the party. Romney, McCain, Bush, Dole, Bush, Ford, Nixon. The only two possible exceptions I can think of in the last 50 years would be Goldwater (definitely not "establishment") and, arguably, Ronald Reagan.