by Karl Kurtz
Ballotpedia, the useful wiki on state elections, recently published a paper, "Anti-Incumbency Voting Patterns in State Legislative Elections," that makes much of an apparently significant increase in primary election defeats of incumbent legislators in 2012 compared to 2010:
Anti-incumbent animosity is making itself felt in state legislative elections. Incumbent members of state legislatures in 2012 are being defeated in primary elections at a rate far higher than in 2010.... [I]n 2010, 8.38 percent of incumbents who faced a challenger in their primary were defeated, while the comparable figure for 2012 is 14.8 percent, for an increase of 76.7 percent.
This makes for a nice trend headline, and Ballotpedia has some great data on incumbent primary defeats to back it up. Trouble is , we know that 2012 is a redistricting year and that the years ending in "2" in every decade have significantly higher rates of turnover. Turnover is greater because more incumbents, faced with the challenge of contesting a newly-drawn district, are likely not to run again, and those who do are more susceptible to primary or general election defeat in their altered districts.
For this reason, I wished that Ballotpedia had compared 2012 primary election defeats to the last redistricting year, 2002, in addition to 2010. When I set out to do this myself, I discovered that we at NCSL do not have data on 2002 primary election defeats (and Ballotpedia wasn't around at the time). But we do have numbers for 2002 pre-election turnover--the combination of incumbent retirements and primary election defeats. By recalculating Ballotpedia's data for 2012, I came up with this table showing pre-election turnover for the 35 states that had held primaries as of Aug. 15, 2012:
8/22/12 correction: The following table has been changed from the original posting to correct data for North Dakota.
This analysis showing a marginal one percent nationwide difference in pre-election turnover between the two redistricting years results in a rather different headline: 2012 pre-election turnover in state legislative races, whether due to retirements or primary election defearts, appears to be typical for a redistricting year.
There are interesting state-to-state variations in these data. First of all, California, which has the highest rate of pre-election turnover, did not have a single incumbent primary election defeat--all of its turnover is due to term limits and retirerments. The effects of term limits (the "TL" column) on turnover are clearly evident in this table as eight of the top 10 states in 2012 have term limits.
In the term-limited states, the cycles of the limits come in different waves, which explains why Michigan and Missouri have much lower pre-election turnover in 2012 than in 2002. Perhaps this also explains how low the term-limited states of Ohio and Oklahoma are on the list in both 2012 and 2002, but I'm not entirely certain.
Kansas' high ranking on the list in 2012 is due to the extraordinary number of incumbent primary election defeats within the Republican party. But why are the rates of turnover in North Dakota more than twice as great in 2012 compared to 2002, given that only four incumbents lost in their recent primary? [8/22/12 correction] In Oregon the reverse is true--the turnover rate in 2002 was nearly twice as great as it is in 2012--but I don't know why.
Readers' contributions on these and other anomalies in the data are welcome.