Gerrymandering structurally suppresses minority and partisan representation

The claim

Partisan gerrymandering is the practice of drawing legislative district boundaries to maximize one party’s seat share relative to its vote share, typically by concentrating opposition voters into a small number of districts (“packing”) and spreading the remaining opposition voters thinly across many districts where they lose narrowly (“cracking”). The structural claim is that this practice functions as a self-reinforcing mechanism: the party that controls the state legislature during the decennial redistricting cycle can engineer a map that insulates its legislative majority from the normal democratic correction mechanism of elections, allowing a political minority — measured by statewide vote share — to govern as a legislative majority for a decade at a time. This dynamic suppresses both partisan representation (parties whose voters are systematically packed and cracked) and, frequently, racial and ethnic minority representation, since the two forms of discrimination are often correlated and sometimes legally indistinguishable.

The mechanism

The mechanism operates through the winner-take-all structure of single-member district systems. In such systems, a party that wins 60% of the vote in a district wins 100% of the representation from that district; the remaining 40% of votes are “wasted” — they produce no representation. A sophisticated gerrymander engineers two types of wasted votes at scale. Packing concentrates opposition voters into super-majority districts (60–80% opposition) where they win by large margins, wasting votes above the 50% threshold. Cracking disperses the remaining opposition voters across multiple districts where they constitute 45–49% of each district, losing narrowly and wasting all of their votes. The mathematical result is that the gerrymandering party can win a majority of seats with a minority of votes.

Nicholas Stephanopoulos and Eric McGhee formalized this mechanism as the “efficiency gap” — the difference in wasted votes between the two parties, expressed as a share of total votes cast. A neutral map produces an efficiency gap near zero; a deliberately gerrymandered map produces a gap of 7–15% or more. Crucially, once a gerrymander is in place, the losing party cannot easily recover through increased turnout or persuasion, because the same district lines that produced the seat deficit also limit where those gains can translate into seats. The structure is self-insulating.

The racial dimension runs through two related doctrines. First, the Voting Rights Act prohibits district maps that dilute minority voting power (racial vote dilution), which led to the creation of majority-minority districts in the 1990s — districts designed to produce Black or Hispanic legislative representation. Second, racial gerrymandering doctrine under Shaw v. Reno (1993) and its successors holds that race cannot be the predominant factor in drawing a district, even if the purpose is remedial. The interaction between these doctrines has produced persistent litigation over whether maps are drawn to pack minority voters for racial or partisan purposes — a distinction the Supreme Court has struggled to maintain when partisan and racial geography are correlated.

The evidence

Quantifying the 2012 seat-vote gap. The 2012 US House elections are the cleanest demonstration of the mechanism at scale. Democrats won 48.8% of the two-party popular vote nationwide but 46.2% of seats — 201 of 435. Republicans won 51.2% of the vote and 53.8% of seats. The 6-point seat-share bonus was not the product of geographic sorting alone. Samuel Wang’s Princeton Electoral Consortium analysis, subsequently published in the Stanford Law Review, found that the seat-vote curve was asymmetric beyond what geographic clustering could explain, and that the asymmetry was concentrated in states where Republicans had drawn the maps after 2010 — specifically Ohio, Pennsylvania, Michigan, Virginia, North Carolina, and Florida. In states using commissions or split legislative control, the asymmetry was substantially smaller.

Wisconsin: the efficiency gap in litigation. The most thoroughly documented single-state case is Wisconsin after the 2011 REDMAP-era redistricting. Republicans controlled the Wisconsin legislature and drew Assembly maps that produced a systematic efficiency gap. In 2012, Republicans won 60 of 99 Assembly seats (61%) on 48.6% of statewide votes. The efficiency gap was approximately 13%. In Whitford v. Gill (2016), the Western District of Wisconsin found the map unconstitutional as a partisan gerrymander — the first federal court to do so in 30 years — relying in part on the efficiency gap as a judicially manageable standard. The case reached the Supreme Court as Gill v. Whitford (2018), which vacated on standing grounds without reaching the merits, leaving the metric legally available but unvalidated. Wisconsin Republicans subsequently retained their structural advantage through the 2020 redistricting cycle.

North Carolina: documented legislative intent. The North Carolina congressional map drawn after 2010, and its successor map drawn after litigation in 2016, provide unusually direct evidence of gerrymandering intent. In the 2016 cycle, Republicans won 10 of 13 congressional seats (77%) on approximately 53% of the two-party statewide vote. Legislative records admitted in evidence in Common Cause v. Rucho revealed that GOP legislators explicitly directed mapmakers to design a 10-3 partisan outcome, with one legislator stating on the record: “I think electing Republicans is better than electing Democrats, so I drew this map to help foster what I think is better for the country.” The federal district court in Rucho found the map unconstitutional. The Supreme Court’s 2019 decision in Rucho v. Common Cause reversed, holding 5-4 that federal courts have no role in adjudicating partisan gerrymandering claims — a structural and legal determination that left the mechanism entirely in place at the federal level while preserving the avenue of state constitutional challenges.

Rucho v. Common Cause and the judicial vacuum. The 2019 Rucho decision is structurally significant because it removed the federal judiciary as a check on partisan gerrymandering entirely. Chief Justice Roberts’s majority held that partisan gerrymandering claims present political questions beyond the reach of federal courts, that there is no “limited and precise” standard for adjudication, and that the remedy properly belongs to Congress or state legislatures. Justice Kagan’s dissent documented that the maps in question were among the most extreme partisan gerrymanders in American history, noted that every lower court to have considered the specific maps found them unconstitutional, and argued that the majority’s conclusion “condemns the country to a government unmoored from the people’s will.” The practical effect of Rucho was to route all future challenges to state courts applying state constitutions — a path that has succeeded in some states (Pennsylvania, North Carolina’s own state supreme court in 2022) and failed in others (Ohio, where the state supreme court struck down maps six times and Republicans defied the rulings while the election calendar ran out).

Independent redistricting commissions: the natural experiment. California adopted an independent citizen redistricting commission by ballot initiative in 2008 (Proposition 11, extended to congressional districts by Proposition 20 in 2010). The 2010 commission-drawn maps increased the number of competitive congressional districts from approximately 3 to 14. Michigan voters passed Proposal 2 in 2018, creating an independent commission; the 2022 election under commission-drawn maps produced a congressional delegation of 7 Democrats and 6 Republicans on approximately 51% Democratic two-party vote — close to proportional. These cases function as policy interventions: the political geography did not change; the map-drawing authority changed, and seat-vote proportionality followed.

Cross-national comparison. The structural cause-and-effect is confirmed by comparing the US to systems that have eliminated winner-take-all district design authority. Germany’s mixed-member proportional (MMP) system allocates a second tranche of seats through party lists to equalize seat share with vote share; the 2021 Bundestag result showed seat-vote deviations of less than 0.2% for major parties. New Zealand adopted MMP in 1996 after a royal commission documented systematic disproportionality under its Westminster single-member plurality system; seat-vote gaps narrowed immediately and persistently. Australia uses preferential (instant-runoff) voting in single-member districts, which reduces but does not eliminate the gerrymandering incentive; its House of Representatives shows moderate asymmetry. Canada and the UK retain single-member plurality but use independent boundary commissions, producing less extreme asymmetry than US state-drawn maps. The pattern identifies the combination of single-member plurality and partisan map-drawing authority as the operative structural variables.

Racial gerrymandering and majority-minority district doctrine. The racial dimension of gerrymandering involves competing structural pressures. The Voting Rights Act’s Section 2, as interpreted in Thornburg v. Gingles (1986), requires that minority voters have an opportunity to elect representatives of their choice, which in practice has meant creating majority-minority districts in areas of racially polarized voting. These districts have produced the largest share of Black and Hispanic congressional representation. However, the same packing logic that creates majority-minority districts can also be used to concentrate minority voters and thereby dilute their influence across a region — the “bleaching” strategy. Shaw v. Reno (1993) introduced a separate cause of action against bizarrely shaped majority-minority districts on equal protection grounds, creating a doctrinal tension that has not been resolved: majority-minority districts are sometimes required by the VRA, sometimes prohibited by the Equal Protection Clause, and the line between the two turns on whether race or partisan affiliation was the “predominant” motive — a question that is empirically difficult when the two are correlated.

Who benefits

The direct beneficiaries of the current structure are the party controlling the state legislature in years ending in zero. The Republican party benefited substantially from the 2010 REDMAP strategy, which was an explicit and coordinated effort to target state legislative races in 2010 in order to control post-census redistricting. REDMAP was organized through the Republican State Leadership Committee, which raised approximately $30 million specifically for state legislative races in targeted states; the investment produced legislative control in Ohio, Michigan, Pennsylvania, Wisconsin, and Florida, all of which subsequently produced maps with large efficiency gaps. Democrats pursued analogous strategies in Maryland (7-1 congressional delegation on approximately 60% Democratic vote) and Illinois. Incumbent legislators of both parties benefit from incumbent-protection maps that reduce competitive districts, increasing tenure and reducing accountability to voters.

Corporate and donor-class interests benefit indirectly when their preferred policy coalition is structurally insulated from electoral accountability. The Koch network’s investment in REDMAP-era state legislative races was substantial and documented through Americans for Prosperity financial disclosures. The American Legislative Exchange Council (ALEC), funded by corporate members including ExxonMobil, PhRMA, and the tobacco industry, operates most effectively in state legislatures — the same bodies that control redistricting. A structurally entrenched legislative majority is a more reliable vector for ALEC model legislation than a legislature subject to competitive elections.

The counter

The steelman case for the current system involves four points that deserve serious engagement. First, the geographic sorting argument is real: Democratic voters are heavily concentrated in urban areas, producing natural efficiency gaps that do not require deliberate engineering. Chen and Rodden (2013) simulated thousands of random maps for Florida and found that geographic clustering alone produces a persistent Republican seat-vote advantage. The structural argument does not deny this; it argues that deliberate gerrymandering adds an additional and separable layer on top of the sorting baseline.

Second, majority-minority districts under the VRA create genuine tension with proportionality objectives. The districts that have produced the largest gains in Black and Hispanic representation are precisely the packed minority districts that reduce those groups’ statewide influence. Lani Guinier’s critique of winner-take-all systems from the left argues that majority-minority districts are an inadequate substitute for proportional representation and may entrench geographic racial sorting. This is a structural critique of single-member plurality itself, not a defense of partisan gerrymandering.

Third, the Rucho majority makes a genuine point that the efficiency gap and related metrics do not specify what level of partisan asymmetry crosses a constitutional threshold — different metrics produce different results, and courts applying different standards would produce inconsistent national outcomes. The remedy Congress has declined to provide (the For the People Act, which would have required independent commissions, passed the House in 2019 and 2021 and failed cloture in the Senate) is arguably more appropriate than judge-made standards.

Fourth, competitive districts have their own costs: they increase electoral volatility, may incentivize candidates to adopt more extreme positions to mobilize base turnout, and do not in themselves guarantee responsiveness to median-voter preferences. The normative argument for proportional representation — which eliminates the gerrymandering problem structurally — is stronger in theory than the argument for more competitive single-member districts, but involves its own tradeoffs in coalition government stability and local representation.

References

Stephanopoulos, N. O., & McGhee, E. M. (2015). Partisan gerrymandering and the efficiency gap. University of Chicago Law Review, 82(2), 831–900.

Wang, S. S.-H. (2016). Three tests for practical evaluation of partisan gerrymandering. Stanford Law Review, 68, 1263–1321.

McGhee, E. (2020). Partisan gerrymandering and political science. Annual Review of Political Science, 23, 171–185. https://doi.org/10.1146/annurev-polisci-060118-045351

Chen, J., & Rodden, J. (2013). Unintentional gerrymandering: Political geography and electoral bias in legislatures. Quarterly Journal of Political Science, 8(3), 239–269. https://doi.org/10.1561/100.00012033

Brennan Center for Justice. (2019). Gerrymandering explained. New York University School of Law. https://www.brennancenter.org/our-work/research-reports/gerrymandering-explained

Rucho v. Common Cause, 588 U.S. 684 (2019).

Whitford v. Gill, 218 F. Supp. 3d 837 (W.D. Wis. 2016).

Grofman, B., & King, G. (2007). The future of partisan symmetry as a judicial test for partisan gerrymandering after LULAC v. Perry. Election Law Journal, 6(1), 2–35. https://doi.org/10.1089/elj.2006.6002

Kousser, T. (2004). Redistricting and the decline of uncompetitive congressional districts. Political Research Quarterly, 57(4), 503–512.

Engstrom, E. J. (2013). Partisan gerrymandering and the construction of American democracy. University of Michigan Press.