Political scientist Boris Shor, who regularly tallies hundreds of thousands of roll-call votes in state legislatures, and who keeps track of polarization in state legislatures, now says California has been overtaken by Colorado as the most polarized legislature. Here are the new rankings.
The rankings bolster other political science research, which has found no correlation between type of primary system and degree of polarization. Among the seven most polarized states are one closed primary state (Colorado); one semi-closed primary state (Arizona); three open primary states (Missouri, Montana, and Texas); and the two top-two states, California and Washington. Although Colorado has recently switched to a semi-closed primary state, all its legislators were chosen in a closed primary system.