Ahead of the 2018 midterm elections, it was widely noted that partisan gerrymandering would diminish the translation of more votes for Democrats into seats in the House of Representatives. Less anticipated was that the effects of pro-Republican partisan gerrymandering would reach historic levels. In states such as North Carolina and Ohio, the 2018 elections saw Republican gerrymanders create biases not seen in decades, making the districting plans in those states the most pronounced pro-Republican gerrymanders in living memory.
To measure the magnitude of partisan gerrymandering, I use the efficiency gap2, the difference in wasted votes for each party. Wasted votes are simply votes cast for a party’s candidates that did not contribute to the winning of a seat: for a party winning a seat, wasted votes are those beyond needed to win the seat; for a party losing a seat, all votes cast there are wasted. The efficiency gap is simply the sum of Republican wasted votes minus the sum of Democratic wasted votes, expressed as a proportion of the total number of votes.
In the table below I show wasted vote calculations and the efficiency gap for 2018 midterm Congressional elections in North Carolina’s Congressional districts, sorting the districts by Democratic vote share, omitting one uncontested district:
| District | Dem Votes | Rep Votes | Dem % | Winner | Dem Wasted Votes | Rep Wasted Votes | Dem % 2016 | Swing |
|---|---|---|---|---|---|---|---|---|
| 4 | 242,002 | 80,546 | 75.0 | D | 80,729 | 80,546 | 68.2 | 6.8 |
| 12 | 202,228 | 74,639 | 73.0 | D | 63,795 | 74,639 | 67.0 | 6.0 |
| 1 | 188,074 | 81,486 | 69.8 | D | 53,295 | 81,486 | 68.6 | 1.1 |
| 9 | 136,478 | 138,338 | 49.7 | R | 136,478 | 931 | 41.8 | 7.8 |
| 2 | 148,959 | 167,382 | 47.1 | R | 148,959 | 9,212 | 43.3 | 3.8 |
| 13 | 128,764 | 145,962 | 46.9 | R | 128,764 | 8,600 | 43.9 | 3.0 |
| 8 | 112,971 | 140,347 | 44.6 | R | 112,971 | 13,689 | 41.2 | 3.4 |
| 7 | 119,606 | 155,705 | 43.4 | R | 119,606 | 18,050 | 39.1 | 4.4 |
| 6 | 122,323 | 159,651 | 43.4 | R | 122,323 | 18,665 | 40.8 | 2.6 |
| 5 | 118,558 | 158,444 | 42.8 | R | 118,558 | 19,944 | 41.6 | 1.2 |
| 10 | 112,386 | 164,060 | 40.7 | R | 112,386 | 25,838 | 36.9 | 3.8 |
| 11 | 115,824 | 177,230 | 39.5 | R | 115,824 | 30,704 | 35.9 | 3.6 |
| State-wide | 1,748,173 | 1,643,790 | 51.5 | 3D:9R | 1,313,688 | 382,304 | 47.7 | 3.8 |
The 2018 results confirm that North Carolina’s districting plan is a brazen pro-Republican partisan gerrymander — described as such by its designers3 — and found to be unconstitutional by a three judge, U.S. District Court panel.4
Democratic votes in North Carolina are disproportionately “packed” into districts 1, 4, and 12, where Democratic candidates win with overwhelming majorities, no more marginal than 70-30 in District 1. Republican votes are efficiently spread through the remaining 9 districts, with Republicans winning by thin margins through to a 60-40 margin in District 11; the Republican candidate also won District 4 unopposed. Across the 12 contested districts, Democrats won 51.5% of the two-party vote, but just 3 seats (25%), a radically disproportionate result. Swings towards Democrats were not small — as high as 7.8 percentage points in district 9, retained by Republicans with just 0.3 percentage points – but insufficient to overcome the pro-Republican gerrymander.
In the nine districts they lost, Democratic votes are effectively “wasted”. Across North Carolina’s twelve contested Congressional districts, the pro-Republican gerrymander results in a much higher wasted vote tally for Democrats than Republicans, a consequence of the “efficiency” of the districting plan’s conversion of Republican votes into Republican seats, relative to the way it maps Democratic votes into Democratic seats. Subtracting Democratic wasted votes from Republican wasted votes and dividing by the total number of votes cast for both parties gives us the “efficiency gap”, which is
\[ \frac{382,304 - 1,313,688}{1,748,173 + 1,643,790} = \frac{-931,384}{3,391,963} = -0.275. \]
Comparisons with other states and previous Congressional elections put North Carolina’s pro-Republican gerrymander in perspective. The -0.275 efficiency gap in North Carolina is the largest pro-Republican efficiency gap score in a set of 531 Congressional election outcomes since 1972, spanning 25 states with 7 or more Congressional districts.
The following table lists the 10 largest efficiency gaps observed in 2018 (among states with at least 7 CDs with both Democratic and Republican candidates).
| State | Efficiency Gap | Rank 2018 | Rank 1972-2018 | Dem Rank 1972-2018 | Rep Rank, 1972-2018 |
|---|---|---|---|---|---|
| NC | -0.275 | 1 | 3 | 1 | |
| OH | -0.224 | 2 | 11 | 7 | |
| NJ | 0.193 | 3 | 25 | 10 | |
| IN | -0.175 | 4 | 43 | 25 | |
| TX | -0.172 | 5 | 47 | 29 | |
| MO | -0.141 | 6 | 70 | 42 | |
| TN | -0.088 | 7 | 184 | 113 | |
| CA | 0.086 | 8 | 192 | 76 | |
| GA | -0.086 | 9 | 193 | 117 | |
| FL | -0.085 | 10 | 198 | 120 |
Ohio…
New Jersey…
In at least 26 US states, redistricting is a political affair, an act of the state legislature, requiring majority approval from the houses of the state legislature and the governor’s assent. In 2011-12, Republicans controlled the redistricting process in 17 of these 26 states and Democrats in 5 states. Earlier this year the Pennsylvania State Supreme Court overturned a Republican-drawn plan and instated a court-drawn plan. Courts or independent redistricting commissions controlled redistricting in 14 states.
The following table shows the frequency of different types of redistricting plans in place for the 2018 midterms, and the number of CDs under each plan. Note that 141 CDs — about 1/3 of the Congress — will be elected under plans drawn by Republican state legislatures and governors. Plans enacted by courts or commissions span 16 states and 224 CDs, or about half the Congress. Democrats controlled the redistricting process in just 5 states spanning 42 CDs, or about 10% of the Congress.
| Control | # States | #CDs | States |
|---|---|---|---|
| Commission or Court | 16 | 224 | AZ, CA, CO, CT, FL, IA, KS, MN, MS, NJ, NM, NV, NY, TX, VA, WA |
| Democratic | 5 | 42 | AR, IL, MA, MD, WV |
| Divided | 2 | 11 | KY, OR |
| Republican | 15 | 141 | AL, GA, IN, LA, MI, MO, NC, NE, OH, OK, PA, SC, TN, UT, WI |
| Small states (1 or 2 CDs) | 12 | 17 | AK, DE, HI, ID, ME, MT, ND, NH, RI, SD, VT, WY |
Under a fair system, each party should have the same chance of forming a majority if they win roughly half of the votes: a symmetry requirement that can be — and should be — supported by the guarantees in the First and Fourteenth Amendments to the Constitution of the United States. This symmetry is manifestly absent from contemporary American elections.
The systematic, deliberate, partisan manipulation of district lines — with the express intent of suppressing the responsiveness of legislatures, laws and policy to public opinion — is a corruption of American democracy. If votes change, but changes in seats, laws and policy are muted, if politicians can insulate themselves from all but large swings — reducing waves to ripples — then should we be surprised that citizens report declining satisfaction with democracy and less faith in its institutions, that democracy’s critics and its enemies are emboldened?
Partisan gerrymandering played a historically unprecedented and politically consequential role in the 2018 midterm elections. Left unaddressed by courts, partisan gerrymandering will continue to poison American democracy.
Professor of Political Science and Chief Executive Officer, United States Studies Centre at the University of Sydney.↩
cite↩
cite↩
League of Women Voters vs Rucho, 240 F. Supp. 3d 376 (M.D.N.C. 2017), decided 9 January 2018. I testified in this case as an expert witness for plaintiffs at trial in late 2017.↩