I like to use plots to illustrate asymmetric polarization in my American Politics courses. A few years ago, I ran into a really great polarization plot, which looked like it was created with the ggridges package in R.
Instead of a poor attempt at updating that plot, I created dumbbell plots for both the House and the Senate in R using first dimension NOMINATE scores and stitched them together using the patchwork package. The plots show that Republicans have moved further right ideologically than Democrats have moved left.
Feel free to use the above plot or pull the R script from github to customize it.
Matthew Gross 