This is a very insightful essay on political discipline.
I am reminded of the focus on faction in Federalist 10, written by James Madison, the most important and influential of the Federalist Papers.
Here is a discussion of faction and self-government by Madison.
And why dems have so much political discipline, by a regular writer at AT. It is actually pretty easy to see–identity and interest politics create cohesion–true believer discipline.