But, of course, 2009 was a high-water mark for Democrats nationally, following the strong Democratic elections of 2006 and 2008. What did the pattern look like going back further, readers wondered.
One reader helped us answer that question. Dr. Carl Klarner, a former professor at Indiana State University, has compiled decades of data on the partisan makeup of each state's legislature -- often stretching back to the 1940s. He shared that data with the Post, which allows us to view the pattern of partisanship stretching quite a bit further back.
According to Klarner's data, there have never been more Republicans serving in state legislatures than there are currently.
Naturally (but not necessarily), the percentage of Republicans in state legislatures is also at a high over the course of his data, stretching back to the 1930s.
You can see the pre-Obama shift to Democrats in the big dip at the upper right of the graph (and then the smaller one in 2012).
The fact that there are so many more Republican-controlled legislatures, predictably, means that legislatures are more heavily Republican than in the past. Nearly half of state legislatures are 20 percentage points more Republican than Democratic, when the partisan leanings of the two chambers are combined.
(Data was not available for all states in each year.)
The long-term shift in the states varies. Southern states moved rapidly from heavily Democratic to heavily Republican during and after the Civil Rights movement. (Some only completed that shift recently.) For example:
Northern states went the opposite direction.
One of the more interesting states is West Virginia, which was consistently and heavily Democratic -- until recently.
(We've included the history of each state below for you to ogle.)
The bigger question is why this shift has occurred. Part of it is that voters have become more Republican since 2008, when the big shifts started to occur. Part of it is that the population in less-Democratic states, particularly in the South and West, is increasing. Part of it is probably legislative gerrymandering.
But we'll leave that question to others -- others who are welcome to follow Dr. Klarner's lead and e-mail any thoughts or data they have at their disposal.
The partisanship in each state over time
Gaps in the graphs indicate data missing from Klarner's dataset.