Redistricting Effectiveness and Delegation Changes
Evaluating district-level and state-level effectiveness of gerrymandering, including likelihood of successful flips of targeted seats, against the 2026 electoral environment and a neutral environment.
Redistricting Effectiveness of Individual Districts
Flip probability and margin shift magnitude across individually redrawn congressional seats.
Active Environment: 2026 Midterm (D+8.0)
State-Level Delegation Changes
Expected value of net seat change against the target of each gerrymandered state.
Active Environment: 2026 Midterm (D+8.0)
Methodology and Metrics Explained(WORK IN PROGRESS - IGNORE FOR NOW)
Partisan Index
Measures the baseline partisan environment of each district. It is computed as a weighted blend of the reallocated 2024 presidential margin and the re-tabulated 2020 presidential return, normalized against national popular vote baselines:
Reported to 1 decimal place as a signed rating (e.g., D +8.5 or
R +55.9). Positive values denote a Democratic advantage; negative values denote a
Republican advantage.
Gerrymander Effectiveness & Durability (GES)
Quantifies how reliably a redraw flips or retains a seat across different national political climates using a logistic win-probability function (σ = 5.5%):
Truncated to [-50, +100]. Positive values indicate an effective gerrymander (>50% win probability), zero represents a toss-up, and negative values denote vulnerability to seat loss during adverse wave conditions.
Edge-Case Handling & Jungle Primaries
Standard two-party general elections do not occur in all seats. To prevent mathematical distortions, we apply a strict 3-tier hierarchy[cite: 2]:
- Standard Contest: Signed two-party margin:
(Dem - Rep) / (Dem + Rep)[cite: 2]. - Top-Two / Jungle Primaries (CA & WA): In general contests between members of the same party (D vs D or R vs R), we aggregate all Democratic vs. Republican votes cast during the all-party primary stage as the benchmark[cite: 2].
- Unopposed / Uncontested: When a major party fielded no candidate, the 2024
Presidential Margin is imputed as the true partisan floor[cite: 2]. Non-standard races are
flagged with an asterisk (
*)[cite: 2].
Impact on Targeted Districts
Definitions for the topline metrics in the default sidebar overview[cite: 2]:
- Mean Partisan Shift: The absolute average shift
(
|Margin Shift|) across all targeted boundaries, measuring the raw magnitude of the cartographic changes[cite: 2]. - Median Partisan Lean: The median partisan lean of all targeted seats, indicating the center of gravity of the redrawn maps[cite: 2].
- Mean Partisan Shift (Net): The directional signed mean
(
Σ Margin Shift / N), revealing which party captured net territory overall[cite: 2]. - Median New District: The exact median seat when sorting all altered districts by post-redistricting presidential margin[cite: 2].
Tipping Point & Seat Advantage
Calculates chamber-control thresholds and spatial seat bias across the 435 U.S. House seats[cite: 2]:
- Tipping Point District: The 218th seat when ranking all 435 congressional districts from most Democratic to most Republican[cite: 2]. If a party wins the tipping point seat, they secure the House majority[cite: 2].
- Generic Ballot Advantage (Seat Bias): Measures systemic cartographic tilt
by subtracting the national popular vote share from the majority party's projected seat
share[cite: 2]:
Advantage = (Seats Won / 435) - National 2-Party Vote Share