On July 23, Political Scientists Boris Shor and Nolan McCarty released an updated study of polarization in state legislatures. They find that California still has the nation’s most polarized legislature, just as it did in 2011, before California has used the top-two system. See here. Washington state has the nation’s fourth most polarized legislature, following California, Colorado, and Arizona.
The data for the updated study can be found here. Shor and McCarty had published their original research in 2011, so the comparison between the new data and the 2011 data is useful for seeing changes.