(I actually think the Republicans are going to nominate the most conservative candidate either way. They just need a thorough butt-kicking to focus their minds before they can move back toward the center.)
I also think that John Boehner will risk his role as Speaker to bring an immigration bill to the House floor. (It's that important to the Republican Party.) But if he can't -- or won't -- then the tea party will be seen as fully in control and there will be no chance of a moderate candidate for 2016.