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Compact districts and Republican bias: further discussion from Michael McDonald

- November 16, 2009

In response to the Chen and Rodden paper, Michael McDonald writes:

I [McDonald] cover the issue of the application of redistricting criteria in the Midwest Mapping Project report available here.

I [McDonald] would quibble with the claim that compact and contiguous districts will “always” generate substantial pro-Republican bias. There are a number of caveats that cannot be addressed by an analysis of Florida’s congressional districts alone.

– It is well-known that single-member district systems tend to provide a seat bonus to the majority party. This bonus may be offset by the inefficiencies of Democrats’ residential patterns, thus producing a plan that has actually little or no bias. This may be true in a heavily Democratic state like Illinois (for the congressional districts), but may
not be true for a battleground state like Florida.

– These biases are most prevalent where the size of the districts to be drawn are smaller than the urban areas where Democrats are concentrated. It is relatively easy to unpack the Twin Cities to draw a balanced congressional plan for Minnesota’s eight congressional districts, but is it difficult to do so for the 134 state legislative lower chamber districts.

– The residential patterns in the state matter, too. Some states like Wisconsin tend to have a relatively balanced mix of Democrats and Republicans (here, in much of the southern part of the state). Thus, congressional districts in Wisconsin following traditional redistricting principles tend to have relatively little partisan bias.

– There is an issue of partisan symmetry to consider, as well. While there may be pro-Republican bias, generally, more Republican districts tend to be competitive. So, Republicans gain some bias in exchange for increased uncertainty. In a large electoral swing such as 2006 or 2008 towards the Democrats, the result can be that Democrats unseat many Republicans in competitive districts, giving Democrats a super-majority in, for example, Minnesota’s Senate even though the plan appears to have a pro-Republican bias.

Generally, I agree that compactness and other traditional redistricting principles tend to work against Democrats, especially in a state like Florida where Democrats are concentrated in a corner of the state. It is for this reason that I have cautioned the proponents of Florida’s redistricting ballot initiative that they may not fully realize their vision of partisan fairness through the application of traditional redistricting principles.

However, these caveats suggest that the pro-Republican bias is not universally true. The truth is more complicated and depends on the jurisdiction, the number of districts to be drawn, and the political circumstances. I recommend that careful consideration be given to the criteria one wishes to adopt for a given jurisdiction. If partisan fairness
is a goal, then as I have published elsewhere, then that criteria should be explicitly stated in the criteria, rather than hoping it will be achieved through seemingly-apolitical means.

And here’s a reference: Michael P. McDonald. 2007. “Regulating Redistricting.” PS: Political Science and Politics 40(4): 675-9.