I’m working on new visualizations of political polarization in American state legislatures in preparation for a conference honoring the work of legendary political scientist Keith T. Poole. Here’s a slopegraph (inspired by Edward Tufte and powered by Thomas Leeper’s awesome R package) of polarization in Southern state legislatures from 1996-2017 (marked in 4 year intervals plus 2017 preliminary data). This was a period of intense transformation in the South, when the almost-fully Democratic-controlled legislatures transformed into Republican-dominated ones in just two decades. Polarization is measured as the distance between the Republican and Democratic party medians, averaged across the two chambers.
In every single state, the parties have been polarizing. And would you just look at Texas? It was the most polarized in 1996, and it’s only increased its lead in 2017.
The line colors represent whether Republicans or Democrats polarized faster in that state. And, in contrast to Congress, Democrats are polarizing faster more frequently than Republicans in the South, including Texas.
Here are the plots for the Republican and Democratic party medians in the South over this time period to give you a sense of how the parties changed. First the Democrats:
Now the Republicans: