I’m working on a paper about a phenomenon called intra-district divergence. It’s a simple idea, coined in a paper by McCarty Poole and Rosenthal (2009) and the idea has probably been given a dozen names at different times, but essentially refers to the difference between the representation of GOP and Democratic legislators for districts with similar partisan characteristics. I live in Oregon’s 3rd district, represented by Earl Blumenauer. If, say, Jamie Herrera Butler (R, WA-03) represented OR-03 instead, you can bet she would generate a different voting record and legislative history. The difference between Bluemenauer and hypothetical-Butler is the intra-district divergence, and there are some imperfect but usable ways we might try to measure it.
Intra-district divergence isn’t necessarily a problem, but a casual observer could ask, “why should Blumenauer and Butler represent this district differently, but for undue partisan pressure?”. Presumably, they would both want to keep their jobs, and they would both need to account for the same hemp-fueled partisan profile in OR-03 to win an election. If you’re bothered by partisan polarization, you need to think about this kind of phenomenon, and try to explain its apparent increase.
The analytical problem, of course, is that we can’t observe this divergence directly. We have to estimate the behavior of hypothetical Butler and compare that guess to the genuine record of Blumenauer. The reality is that OR-03 will not elect a Republican any time soon, so this projection about Butler requires a few awkward assumptions about district partisanship and legislator sensitivity to it.
But we can observe bona fide divergence in a few special instances: U.S. state legislatures with multi-member districts. Usually, we elect one house member for each state legislative district, but four U.S. states (New Jersey, Arizona, South Dakota* and Washington) elect two per district exclusively. Ten states elect some or all of their members in this fashion. The practice used to be more typical and is dying out, but it means we might, occasionally, stumble into situations where a multi member district has elected one Republican and one Democrat. Here’s a scatterplot showing the
current 2013 Washington State House, comparing district members to those district’s 2012 Obama presidential vote share:
Washington state has 49 legislative districts and elects 98 state representatives. The vertical axis on this graph uses measure of legislator ideology called the NPAT score, and it’s based on the same technique known as DW-NOMINATE that you often see applied to Congress, using roll calls and adjusted for some survey data (see this updated dataset described by Shor and McCarty 2011). Points that appear higher on this plot (arbitrarily chosen) reflect a more conservative voting record, and unsurprisingly, Republicans in red appear on the top and Democrats in blue appear on the bottom. The left hashed vertical line represents 50% support for Obama in 2012; the right hash line represents the 56.2% that Obama won in Washington state.
Notice that each point has a vertical twin with the same Obama 2012 Percent. Most districts elect two members from the same party, even though Washington has a top two primary system. But some districts elect from one each party, and I have enlarged and numbered those districts in the plot. Let’s call these “blended districts”.
With a couple of exceptions, you can see that the divergence (the gap between the Republican and the Democrat) is essentially the same for the blended districts. Elect a Democrat, you get a liberal, and elect a Republican, you get a conservative, and the other distinctions pale.
Two exceptions are worth noting. You see more conservative-than-usual points for the Democrats elected in Districts 17 and 31. These districts elected one Democrat, even though most voters chose Romney over Obama. Look here for all the 2014 results. The District 17 Democratic represenative was Monica Stonier. For her trouble, as she tried to
contort adapt her voting record to the conservative bent of her Vancouver, Washington district, while undoubtedly angering her Democratic caucus, she was defeated in 2014 by a Republican (51.6% to 48.4%). The District 31 Democratic representative is Christopher Hurst, whose record was even more conservative than Stonier’s. Hurst barely won reelection by the percentages of (I kid you not): 51.6% to 48.4%.
The bottom line: look to the “D” or the “R” for the most important information about the way your representative is going to perform. Resist claims to the contrary, implied or otherwise. (see PPS below).
* South Dakota splits one of its districts into two subdistricts.
PS: You might say, “if we think of states in the U.S. Senate as districts, they they, too, are multimember”. The problem with analyzing the Senate this way is a) they don’t elect their two members in the same year and b) it’s the U.S. Senate, which for a variety of reasons, is an idiosyncratic, single point of comparison.
PPS: Monica Wehby was the Koch-fueled Republican challenger to Oregon’s U.S. Democratic Senator Jeff Merkeley in 2014. Since she’s a doctor, she was clearly the best choice for bi-partisanship, just like Dr. Paul Broun (GA-10).