Republican Presidential nominee Donald Trump has repeatedly suggested that the US Presidential election could be “rigged” or “stolen”. There is, of course, little evidence for these allegations about the Presidential election. However, there is abundant evidence that the elections to the lower house of the US Congress are effectively predetermined. This is the result of partisan gerrymandering of the House of Representatives – the way that politicians in state governments draw the Congressional districts. We predict that the Republican Party will retain control of the House of Representatives in 2016 (and 2018 and 2020), even if Democrats win a considerable majority of the national Congressional vote. How is it that the chamber supposedly responsive to “The People Alone” can be so insulated from popular sentiment?
In our book, Gerrymandering in America, we present evidence that the Republican Party’s advantage in the House is the result of deliberate partisan gerrymandering by state legislatures. We analyzed the current congressional districting plans, which were produced after the 2010 Census, and compared them to the plans drawn in the previous districting cycle, and find that there is a pro-Republican advantage overall. This advantage means that, short of a Democratic landslide of 54-55%, resembling Obama’s sweeping victory in 2008, the Republican Party’s hold on the House is virtually assured.
The United States has single-member district elections and a two-party system. Of course, this disproportionately rewards the larger party. However, we can measure how much each party is treated the same under similar circumstances. This is how the partisan symmetry measure addresses bias in districting. In a nutshell, it asks: if Party A gets (say) 55% of the vote and is awarded 60% of the seats, would Party B also get 60% of the seats if it won 55% of the vote? We calculate the difference between the number of seats the Democrats would get for 55% and the number of seats the Republicans would get for 55% of the vote. We do this for every level of support between 45% and 55% and take the average.
This approach does not consider whether there is perfect proportional representation between the parties – only whether they are treated equally. In a symmetrical districting plan, both parties get an equal opportunity to enjoy the unequal rewards of “winner-take-all” elections.
Using the partisan symmetry measure, we analyzed the level of partisan bias in each state’s congressional plans, both for the post-2010 maps and the earlier maps (produced after 2000). We calculated seats/votes functions on the assumption of uniform partisan swing – if a party gains 5% nationally, it gains 5% in every district, give or take an allowance for local factors (simulated through random disturbances). We calculated the level of support the Democrats would win in each district if they won 50% of the national vote, given the national level of support for the party in actual elections. Then we varied the level of national support, generating a thousand simulated elections for each hypothetical vote swing with different random local effects for each district. This produced the seats/votes function in the graphs below. From this we calculated the symmetry measure.
Figure 1: Seats/Votes function for Congress 2002-2010
Figure 2: Seats/Votes function for Congress 2012
Figures 1 and 2 show the seats/votes functions under the 2002-2010 districts and the new districts used in 2012 elections. What is striking is the difference in bias between the old plans and the new plans. In the 2002-2010 district plans, we observe a 3.4% asymmetry nationwide. Although this level of bias is statistically significant, it is only modest in comparison to the 2012 plans, in which we observe 9.4% asymmetry in favor of Republicans—a nearly threefold increase.
Another way to grasp the increased bias in the new districting plans is by looking at the seats/votes function when it reaches the 50% Vote mark. In a perfectly unbiased plan, a party gains about 50% of the seats for a 50% vote share. In Figure 1, the seats/votes line comes reasonably close to this mark, and the bias is low—less than 2% at 50% of the vote. By contrast, in the 2012 plans, the line crosses the 45% Seat mark at 50% of the vote, which indicates about 5% bias at the 50% vote mark.
One of the immediate consequences of unrestrained partisan gerrymandering is that, short of a landslide Democratic victory resembling 2008, when multiple factors were favorably aligned for the Democrats, the Republicans are very likely to retain control of the House through 2020. But one of the more profound consequences is that redistricting jeopardizes one of the bedrock principles of the Constitution, that of popular control over the House. The current districting climate means that politicians are free to choose their voters, thus upending the relationship between democratic citizens and their elected officials. Without intervention by the courts, political parties are free to manipulate House elections to their advantage without fear of consequence.
Anthony J. McGann is Professor of Government and Public Policy at the University of Strathclyde; Charles Anthony Smith is Professor of Political Science at the University of California, Irvine; Michael Latner is Associate Professor of Political Science at the California Polytechnic State University, San Luis Obispo; Alex Keena is a Visiting Lecturer at the University of Richmond. Their book Gerrymandering in America: The House of Representatives, the Supreme Court, and the Future of Popular Sovereignty (Cambridge University Press) is available now.
Image: Matt
