Romney kept out big challengers in 2008 by pulling huge fund raising stunts very early, and letting it be known that he would self fund if needed and that he had a huge labor force behind him (many of them Mormons), he still lost to two unfunded light weights though.
Romney has shaped the primary field for 7 years.
Neither of those qualify as "the GOP establishment picking our candidate", which was the theory I see put forward that I just don't agree with.