No one can doubt that this establishment v insurgent dynamic has been present in Congress for a while, but “DW-nominate” scores indicate that this dichotomy is becoming increasingly important. These scores seek to rank congressional members’ ideology in two dimensions, based on their rollcall voting record. In my previous analyses of polarization, I’ve used the first dimension, which usually does a good job at placing members on the liberal-to-conservative spectrum. The second dimension has rarely been used in recent years because it hasn’t seemed to stand for anything.

In the past Congress, however, the second dimension has begun to have more explanatory power – among Republicans, especially. That is, something beyond just being conservative or liberal is beginning to predict voting patterns of congressmen and women. The vote-view folks and I think that this dimension is along an establishment v anti-establishment axis, though one might also argue that it is geographically based – since many insurgent Tea Party members are from the American south. …

If the voting had been strictly along partisan lines, we’d expect the best fit line to be straight up and down. That is, the vote could easily be determined as being to the left or to the right. Instead, we have more of a diagonal line that goes from upper left to lower right in the House and upper right to lower left in the Senate. What that means is that there are liberal and conservative elements behind the voting, but there is also something else happening. You might call it a rather strange vote in which the Tea Party caucus, progressive caucus, and black caucus voted all together – though, arguably, it could be explained as establishment House Democrats and establishment House Republicans voting together. In other words, how many times can we expect John Boehner, Eric Cantor, Steny Hoyer, Kevin McCarthy, Nancy Pelosi, and Debbie Wasserman-Schultz all to vote the same way on a relatively divided debate?