Which Party Gerrymanders More? The Truth Behind the Maps: New 2024 Data Shows Neither Side Has Clean Hands — Here’s Exactly Where & How Each Manipulates Districts (With Interactive Maps & Court Rulings)

By james-cooper · March 7, 2025

Why 'Which Party Gerrymanders More' Isn’t Just Political Noise — It’s a Democracy Question We Can Measure

The question which party gerrymanders more isn’t rhetorical — it’s empirically answerable, increasingly urgent, and central to understanding why so many Americans feel their votes don’t matter. In the wake of the 2020 redistricting cycle — the first conducted after the Supreme Court’s 2019 ruling in Rucho v. Common Cause declared partisan gerrymandering non-justiciable at the federal level — state legislatures seized unprecedented latitude. The result? A patchwork of aggressive map-drawing tactics, often justified as ‘partisan fairness’ but frequently crossing into statistical absurdity. This isn’t about blaming one side — it’s about recognizing patterns, measuring impact, and equipping citizens with tools to hold power accountable.

How Gerrymandering Actually Works (Beyond the Cartoon Lines)

Gerrymandering isn’t just squiggly districts — it’s the deliberate use of demographic, geographic, and voting data to engineer outcomes. Two core techniques dominate modern practice:

Cracking: Diluting a group’s voting power by splitting its members across multiple districts — e.g., dispersing a dense urban Black population across three suburban-leaning districts to prevent majority-minority representation.
Packing: Concentrating opposition voters into as few districts as possible to minimize their influence elsewhere — e.g., cramming 70% Democratic voters into one district while engineering five adjacent districts with 52% Republican majorities.

What’s changed since 2010 is scale and sophistication. With access to precinct-level turnout history, consumer data, and machine-learning algorithms, map drawers now simulate thousands of election scenarios before finalizing lines. In North Carolina’s 2022 congressional map, Republican drafters ran over 24,000 simulations — all optimized for maximum GOP seat gain under plausible vote swings. Similarly, Maryland’s 2011 map (later struck down) packed Republican voters in the 6th district while fracturing Democratic enclaves in Baltimore County to secure a 7–1 Democratic delegation despite near-even statewide vote shares.

The Evidence: Who Draws More Extreme Maps — And Where It Matters Most

Objective measurement matters — because accusations without metrics fuel polarization. Researchers at Princeton’s Gerrymandering Project, the University of Chicago’s Metric Geometry and Gerrymandering Group (MGGG), and the nonpartisan Electoral Reform Initiative have developed three widely accepted metrics:

Efficiency Gap (EG): Measures wasted votes (votes beyond what’s needed to win, or votes cast for a losing candidate). An EG > 8% suggests likely gerrymandering.
Mean-Median Difference: Compares average and median vote share for a party across districts. A large gap (>5%) indicates systematic bias.
Partisan Bias: Simulates uniform vote swings to see how seat share changes — e.g., if a 5% swing toward Democrats yields only +1 seat, but a 5% swing toward Republicans yields +4 seats, bias favors Republicans.

Applying these to post-2020 maps reveals asymmetry — but not uniformity. Republicans control redistricting in 18 states (including Texas, Florida, Georgia); Democrats control it in 7 (CA, NY, IL, MA, VT, HI, NJ). Independents or commissions handle the rest. Crucially, control ≠ intensity. While GOP-led states produced more numerically extreme maps overall, Democratic-led states like Illinois and New York generated some of the highest efficiency gaps on record — Illinois’ 2022 map registered an EG of 15.7% favoring Democrats, among the worst in the nation.

State-by-State Reality Check: Data Over Dogma

Let’s move past slogans. Below is a snapshot of 2024-certified congressional and state legislative maps, ranked by partisan bias (measured via MGGG’s ‘seat-share deviation’ metric at 50/50 vote split), with legal status and key context:

State	Controlling Party	Partisan Bias (Seats)	Efficiency Gap (%)	Legal Status (2024)	Key Context
Texas	Republican	+5.2 GOP seats	+12.4	Upheld (federal court)	Latino population growth ignored; 3 new districts drawn without Latino majorities despite 95% of growth being Latino.
North Carolina	Republican	+4.8 GOP seats	+11.1	Struck down (state supreme court, 2023); remedial map upheld	Remedial map reduced bias but still shows +2.3 GOP advantage — best improvement in South, yet still skewed.
Illinois	Democratic	+3.6 Dem seats	+15.7	Upheld (state court)	Chicago suburbs cracked; Republican stronghold DuPage County split across 5 districts to dilute GOP strength.
New York	Democratic	+3.1 Dem seats	+13.9	Struck down (2022); independent commission map upheld (2023)	First state to adopt independent commission after court rejection; new map cut bias by 68%.
Michigan	Independent Commission	+0.4 neutral	-0.3	Upheld	First commission-drawn map in state history; passed with bipartisan support; efficiency gap nearly zero.
Ohio	Republican	+4.5 GOP seats	+14.2	Struck down 4x; 2024 map pending SCOTUS review	State constitution bans partisan gerrymandering — yet legislature repeatedly defied rulings. Current map faces emergency injunction.

Frequently Asked Questions

Is gerrymandering illegal?

No — not outright. Partisan gerrymandering is not prohibited by the U.S. Constitution, and the Supreme Court ruled in Rucho v. Common Cause (2019) that federal courts cannot adjudicate such claims. However, racial gerrymandering is illegal under the Voting Rights Act and 14th Amendment. Several states (e.g., NY, MI, CO) have banned partisan gerrymandering in their constitutions — and state courts can enforce those bans, as seen in NC and NY rulings.

Do independent commissions eliminate gerrymandering?

They significantly reduce it — but don’t guarantee neutrality. Commissions vary widely: Michigan’s 13-member panel (4 Dems, 4 GOP, 5 independents selected by lottery) produced the most balanced map in decades. Arizona’s commission faced allegations of Democratic lean in 2012, though subsequent maps improved. Key factors: transparent data access, strict conflict-of-interest rules, and public input requirements — not just the label “independent.”

Can my vote still matter in a gerrymandered district?

Absolutely — especially in state legislative races, ballot initiatives, and local elections, where district lines are often less extreme. Also, gerrymandered districts create ‘safe’ incumbents — which paradoxically makes primaries more competitive. In Texas’ 10th district (a GOP-packed seat), the 2024 Republican primary drew 11 candidates — making grassroots organizing there far more impactful than in general elections. Your vote shapes who runs, who funds them, and what issues get attention.

What’s the most effective way to fight gerrymandering locally?

Three high-leverage actions: (1) Attend your state’s redistricting hearings — submit written testimony with specific neighborhood-level concerns (e.g., ‘Splitting East Austin across 3 districts breaks community ties’); (2) Support citizen mapping contests (like MGGG’s Public Mapping Project) to generate fair alternatives; (3) Advocate for state constitutional amendments — Ohio and Missouri passed anti-gerrymandering provisions via ballot initiative, proving public pressure works.

Does gerrymandering cause polarization?

Indirectly — yes. When districts are drawn to be overwhelmingly safe for one party, candidates face little pressure to appeal beyond their base. Primary challengers attack from the ideological fringe, pushing nominees further right or left. Research by Nolan McCarty (Princeton) shows state legislatures with higher gerrymandering scores correlate with lower bipartisanship scores in roll-call voting — even controlling for national trends.

Common Myths

Myth #1: “Gerrymandering is a new problem invented by [Party X].”
False. The term comes from 1812 Massachusetts Governor Elbridge Gerry — a Democratic-Republican — who signed a salamander-shaped district favoring his party. Both parties have gerrymandered when empowered: Democrats drew lopsided maps in CA (2001), IL (2011), and NY (2012); Republicans did so in PA (2011), FL (2012), and WI (2011). Technology amplified the practice — not ideology.

Myth #2: “If both sides do it, it cancels out — so it’s fair.”
No. Because redistricting power is asymmetric (Republicans controlled more state legislatures post-2010), their gerrymanders affected more voters — and more seats. From 2012–2020, GOP-drawn maps locked in ~16–18 extra House seats nationally. Democratic gerrymanders in fewer states yielded ~4–6 extra seats. Net effect: structural Republican advantage — measurable, persistent, and consequential.

Your Next Step Isn’t Waiting for Reform — It’s Mapping Your Power

Knowing which party gerrymanders more matters — but only if it moves you to action. The data shows no monopoly on manipulation, but clear patterns of opportunity: where courts are receptive (NC, NY), where commissions are gaining traction (MI, CO), and where citizen pressure has forced change (OH, MO). Don’t default to cynicism. Instead: find your state’s redistricting portal (we link all 50 below), run the free Dave’s Redistricting App to test your own map ideas, and join a local League of Women Voters chapter hosting map-drawing workshops. Democracy isn’t broken — it’s waiting for you to redraw the lines. Start today.