One of the more interesting plotlines from this past congressional redistricting cycle involved a dilemma faced by Democratic legislators in Democrat-controlled states. Between the 2010 and 2020 cycles, the increasingly blue states of Colorado and Virginia adopted independent commission systems, taking the power to draw congressional district lines out of the hands of the states’ legislatures and governors. In June 2021, Politico coverage cast this as “unilateral disarmament.” If Republicans were going to retain control over redistricting processes and would use that power to pass skewed maps, the thinking went, Democrats would have to play the game too — even if they believed in ideals of fair and equal representation.
For the most part, that’s what happened. As an April 2022 Vox headline put it, Democrats “learned to stop worrying and love the gerrymander” in states where they controlled the redistricting processes. The efforts of Democratic-controlled governments in New Mexico, Illinois, Nevada, and elsewhere rightfully attracted this sort of coverage. Meanwhile, though, Republicans in states like Florida, Ohio, and Tennessee were proposing and passing maps that overrepresented their own party.
So, at election time, how did the two parties’ efforts ultimately measure up? To get a better sense of this, I compiled data from FiveThirtyEight’s redistricting tracker and Loyola Law School’s “All About Redistricting” database, supplementing it with further information from media coverage of the redistricting processes when necessary. When it comes to measuring how advantageous a given state’s map was towards one party or the other, I chose to use the efficiency gap, a metric introduced in 2015 by Nicholas Stephanopoulos and Eric McGhee, and calculated for the 2022 maps using 2020 election data by FiveThirtyEight.
The intuition behind the efficiency gap is that when a state’s population is partitioned into different congressional districts, voters are allocated in ways that could be advantageous or disadvantageous to their party. When a party wins a district by an especially large margin, many of their voters are not making a difference because the party has already won regardless. The most efficient allocation of voters a party could make is thus one that spreads its voters out to achieve majorities in as many districts as possible.1 When a map helps one party in this way, the efficiency gap will be bigger in size, representing that party’s “undeserved seat share.”
Looking at the set of congressional maps used in the 2022 election, sorted by which body was ultimately responsible for drawing them, a pretty clear story emerges:
First, commissions and courts seemed to produce maps that were less advantageous for either side. This is good news for people who contend that such bodies can be trusted to create fairer maps. (Of course, partisan efficiency gaps only measure one aspect of what it means for a map to be fair or unfair.)
Second, the median efficiency gap for a Democratic map was +17% for Democrats; the median efficiency gap for a Republican map was +15.5% for Republicans. When given the opportunity, both parties tended to produce maps that were advantageous to their own side.
But third, Republicans had far more opportunities to do that.
You can chalk this up to any number of factors: Democrats in New York got really ambitious and their gerrymander was struck down. Republicans in Ohio and Utah were able to neuter their states’ independent commissions, then pass their own skewed maps. And Virginia and Colorado got super fair commission-drawn maps instead of Democratic gerrymanders that could have been. I could go on. Look at California: 52 congressional districts, more than one-tenth of the House, were determined not by the state’s Democratic governor and legislature, but by a squeaky-clean independent commission.
This asymmetry in opportunities to gerrymander sets up an uncomfortable situation for Democrats who earnestly believe in fair representation. If we take for granted that Republicans will tend to draw skewed maps when given the opportunity, and recognize that they enjoyed more of those opportunities, Democrats were effectively starting from behind.
And it’s not merely that Democrats were incentivized to compete against Republican gerrymanders: there was a tradeoff between fair partisan representation within a state’s congressional delegation, versus fair partisan representation within Congress as a whole. A map that helped Democrats by gerrymandering a state into a bizarre collage of politically advantageous shapes actually made Congress more closely resemble the nation in terms of overall partisanship.
Democrats who control state governments can’t do much to get rid of the tradeoff. Commission systems seem quite popular with voters and, to my knowledge, have not seen any retrenchment in blue states in the past couple decades. Any real state-level solutions would have to come about in states where Republicans currently control the redistricting processes — perhaps by establishing independent commissions via ballot initiatives. Absent some coordinated federal solution or a drastic partisan realignment, this state of affairs is likely to continue.
This is not the sort of thing you would hope to see in a healthy democracy. But in our system of single-member-district, place-based representation where state governments determine how seats in the federal legislature are apportioned, and where highly polarized and nationalized political parties interact with these structural features, it’s what we get. If a Democratic state legislator in Illinois wanted the U.S. House of Representatives to more closely reflect voters’ partisan preferences, the most they could do in service of this aim is cut their own state up into hyper-efficient ribbons of blue.
McGhee and Stephanopoulos write that, assuming equal-population districts and using two-party vote shares, the efficiency gap for a given state is equal to “the share of all seats held by a party, minus 50 percent” minus double “the share [of votes] received by a party, minus 50 percent.” Positive efficiency gaps correspond to electoral advantages for the party in question, while negative ones correspond to disadvantages. Here’s a link to a more detailed explanation.
Because of our single-member-district system of representation, the political geography of a state can be more or less conducive to large efficiency gaps. For example: if a state is reliably Democratic, and Democratic voters are spread out geographically in such a way that the party will have majorities in any contiguous congressional district, that state’s map will be very efficient for Democrats no matter who draws the lines. (This state, by the way, is Massachusetts.)