John Farrell has a take on polarization in the National Journal. It’s a really interesting read and I recommend it, particularly if you are interested in the electoral forces at work in polarization. There are several quotes from notable political scientists such as Keith Poole, Catherine Rudder, Thomas Mann, Norm Ornstein, among others. Each year since 1982 the National Journal has rated legislators and measured polarization. The ratings are different than traditional DW-Nominate data the political scientists typically use. Now, there are some issues with their methodology. First, they look for votes that illustrate ideological distinctions between the parties. Second, they eliminate non-controversial votes. And third, they eliminate votes that divide along regional lines. After it’s all said and done, 11% of votes in the House and 41% of Senate votes were included. So, in a lot of ways, this rating is somewhat rigged to illustrate polarization. It does eliminate a lot of procedural votes – which could be advantageous – but isn’t very inclusive of votes that could demonstrate greater commonality than these scores might suggest. But rather than try and illustrate the potentially counter-intuitive point – we may be less polarized on policy substance than many believe (just look at Ezra Klein's recent post, for example) – they reinforce conventional wisdom.
Farrell’s take leans on Nelson Polsby’s 2004 book, How Congress Evolves. In sum, Polsby argues that the development and expansion of air-conditioning in the South amplified the southern migration. As more northerners made the South their home, the once solid South slowly started to turn Republican. Other factors such as Civil Rights legislation in the mid-1960s also helped transform the South from a solidly Democratic region to a predominantly Republican region.
Of course, the elephant in the room is legislative procedure, which has a significant and strong effect on polarization. Without this nuance, a lot of electoral explanations fall short. For example, this particular article highlights the moderating influence of the solidly Democratic South prior to air-conditioning, etc, had a moderating effect on polarization. However, the South was also solidly Democratic from 1879~1910, the other congressional era of intense partisan polarization.
Regardless, Farrell does justice to a lot of interesting political science. It is a very interesting piece with a lot of insight into American history and congressional politics. Well worth your time.