It is now axiomatic that Marco Rubio is the "establishment" favorite in the 2016 Republican primaries, due for a collision with a conservative alternative such as Donald Trump, Ted Cruz, or Ben Carson. But if Rubio really represents the new GOP "establishment," then the fight is over and the conservatives won. Despite infuriating many grassroots conservatives by pushing the failed Gang of Eight immigration-reform bill and advocating a path to legalization, Rubio has an indisputably conservative record as a senator. This is a man who has a lifetime ACU rating of 98 out of 100. A man who has a...