Testimony before NJ State Redistricting Commission

Given the conjunction of these two patterns, it seems natural to draw a link; namely, the increased polarization of Congress is a direct result of the increasing ease of reelection.  Presumably in an era of declining competition politicians no longer feel the need to reach out to moderate and independent voters.  Instead politicians are free to pander to their base. Politicians who do not pander may face primary challenges by ideologically purer candidates.

Is there a link between increased polarization and declining competition? Scholars have yet to establish a compelling causal relationship.  Some scholars (as well as pundits) claim that the link between polarization and declining competition is rooted in the increasingly sophisticated techniques deployed during the congressional redistricting that follows each decennial census. Pundits proclaim that we are in "the age of gerrymandering."   Many observers argue that redistricting increasingly produces districts that are homogeneous with respect to partisanship and voter ideology.  Consequently only conservative Republicans can win in conservative Republican districts just as liberal Democrats dominate liberal Democratic districts.  Because redistricting no longer produces moderate, bipartisan, or heterogeneous districts, moderates cannot win election to the House.

This narrative is attractive not only because of analytical elegance, but because it suggests a single, perhaps even feasible, solution to what ails the American polity --  take the politics out of redistricting.  Draw districts heterogeneous, competitive, and politically moderate.  Appealing to independents would become the key to winning election, and polarization would become a thing of the past.

Unfortunately, although elegant in description and prescription, the story may not be true. There is little empirical support for the claim that districting has had a substantial impact on polarization. 

      That the U.S. Senate has experienced an increase in polarization at the same time as the U.S. House suggests that gerrymandering plays at best a modest role.   In addition to this historical claim, my research (published in the American Journal of Political Science) has three findings that also undermine any such link.

·        First, a very large fraction of the polarization in the U.S. House is the result of what we call  within-district divergence between the voting records of Democrats and Republicans.  In other words, for a given type of district (in terms of partisanship, demographics, ect, a Republican representative compiles an increasingly more conservative record than a Democrat does.  This effect has been the overwhelming source of the increase in polarization since the 1970s, Gerrymandering cannot account for this form of polarization.  

·        Some of the increase in polarization is due to an increase in the congruence between a district's characteristics and the party of its representative.  Republicans are more likely to represent conservative districts and Democrats are more likely to represent liberal ones . Such an effect is consistent with the gerrymandering hypothesis but it is also consistent with a general geographic polarization of voters along ideological and partisan lines.  Moreover, we find that the timing of this sorting effect is inconsistent with the gerrymandering story.  It occurs in the 1980s and early 1990s, relatively early in the upswing of polarization. This is well before the most recent decline in electoral competition in the House. 

·         Next, we simulate the expected polarization following various districting procedures. The difference between the actual polarization and these simulated procedures allows us to estimate the effects of  gerrymandering on polarization. Our upper bound estimate is very small and realistically can account, at most, for 10-15% of the increase in polarization since the 1970s.

·        True, electoral sorting has increased over time, as shown in table 2. But the secular increase in sorting does not appear to be linked to census triggered redistricting that would reflect gerrymanders. A good deal of the increase reflects the gradual disappearance of the one-party South and increased geographical sorting on political and social attitudes.  Moreover, the secular increase in polarization is not primarily a phenomenon of how voters are sorted into districts.  It is mainly the consequence of the different ways Democrats and Republicans would represent the same districts.

Our simulations further demonstrate that the levels of polarization we observe are quite consistent with congressional districts representative of the states for which they are drawn.  Thus, the scope of districting reform to eliminate polarization is extremely limited.  Even if we eliminated districting all together and elected candidates statewide, we could only roll polarization back to the level of the mid-1990s.

Indeed, if anything, we underestimate the ability of redistricting to reduce polarization. Redistricting with an eye to increasing electoral competition will create a large number of districts that are heterogeneous with respect to income, race, ideology, and other characteristics. Recent research indicates that legislators from these heterogeneous districts are likely to deviate, in a polarized fashion, from the "average" preferences of the constituents.

So I conclude with two pieces of general advice for the commission. 

• It's important not to overemphasize the creating electorally-competitive districts for the sake of reducing legislative partisanship and polarization.  Doing so is unlikely to have the desired effects, and artificially heterogeneous districts may be counterproductive.

•  The normatively derisible approach to districting in my view is to have the distributions of districts look like then distribution of voters.  So the number of conservative districts should reflect the percentage of conservative voters, the number of moderate districts should approximate the distribution of moderate voters, and the number of liberal districts should reflect the number of liberal voters.  Legislatures should be representative of the voters.