Getting back to polarization: As I mentioned earlier today, to the extent governing isn't working well today I very much agree with Sean Theriault that "partisan warfare is the problem" (see also Ed Kilgore). The trouble with Washington isn't that the parties are each internally cohesive or that Democrats are too liberal or Republicans too conservative. The problem resides in a Republican Party that too often treats hostility to compromise as an end in itself, and that has come to value destroying opponents more than enacting its public policy preferences. (Theriault properly uses Republican Senator Ted Cruz of Texas as an example of this mindset.)
So how did Republians get that way? It basically comes down to two names: Newt and Rush.