Show letter grades for bias in gerrymandered maps for the top 20 worst offenders.
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Executive summary
You asked for “letter grades for bias” for the top 20 worst gerrymandered maps. Available sources point to two established grading tools — Princeton’s Gerrymandering Project (the Redistricting Report Card) and PlanScore — which assign letter grades or numeric scores using multiple metrics and expert review [1] [2]. No single, consolidated list of “top 20 worst offenders” with Princeton-style letter grades appears in the provided search results; specific state- or map-level grades are available from Princeton’s report card and PlanScore, but aggregated top-20 ranked lists are not found in current reporting [1] [2].
1. Why grading systems matter — and which ones exist
Measuring gerrymanders requires quantitative metrics and local expertise; Princeton’s Gerrymandering Project built a Redistricting Report Card that produces letter grades (A–F, Ins) by combining analytics with reviews from 75 advanced mappers to reflect local geography and context [1]. PlanScore offers complementary numerical analysis using four measures — efficiency gap, partisan bias, mean-median difference, and declination — and produces scores for new plans and historical comparisons [2]. These two systems are the primary tools cited in the sources for translating raw map effects into accessible grades or scores [1] [2].
2. What these grades signify in practice
Princeton’s letter grades are shorthand: A = Good, B = Better than average with some bias, C = Average, D/F = Poor, Ins = Insufficient data [3]. PlanScore’s system does not use simple letters in the snippets but relies on the four statistical measures to indicate partisan advantage and to estimate how many seats a map “gains” for a party [2]. Both approaches recognize gerrymandering manifests as “packing” and “cracking” and translate those behaviors into metrics that can be compared across states [1] [2].
3. Where the worst bias shows up today — what the reporting says
Recent reporting and analysis identify concentrated Republican advantages in multiple states — especially across the South and Midwest — producing strong partisan bias in congressional maps [4]. State-level litigation and political fights in 2025 focused on places like Texas, Alabama, Indiana and others where new maps or mid-decade redistricting efforts produced claims of racial or partisan gerrymanders [4] [5] [6]. The Guardian and Brennan Center note Texas’s 2025 mid-cycle map is viewed by critics as an extreme example of bias and racial sorting; Princeton has graded some maps in that realm among the worst in the nation, according to secondary reporting [6] [7].
4. Limits in available reporting — why I can’t deliver a definitive “top 20” list
Your exact request — a ranked top 20 with Princeton-style letter grades for “worst offenders” — is not present in the supplied sources. Princeton’s Redistricting Report Card exists and assigns letter grades [1] [3], and PlanScore provides detailed metrics [2], but none of the provided snippets contain a ready-made, sourced top-20 list with each map’s letter grade. Therefore I cannot invent or assert a 20-entry ranked table; available sources do not mention a consolidated top-20 with grades [1] [2].
5. How you can get the exact list you want — practical next steps
To create a verifiable top-20 list with letter grades: (a) consult Princeton’s Redistricting Report Card state-by-state pages and export their congressional/legislative letter grades [1]; (b) cross-check with PlanScore’s map scores and historical seat-gain estimates for the same plans [2]; and (c) where mid-decade maps exist (e.g., Texas 2025) factor in litigation summaries from Brennan Center or major outlets to note disputed or racially charged findings [4] [5] [6]. The World Population Review aggregates some of these grades and explains Princeton’s scale, but warns 2025 adjustments may not yet be fully analyzed [3].
6. Competing perspectives and hidden agendas
Experts differ on interpretation: academic projects like Princeton emphasize neutral analytics plus local expertise [1]; advocacy groups such as Brennan Center frame gerrymanders as systematic threats favoring one party and harming voters of color [4] [5]. Political actors sometimes argue maps are lawful partisan politics; courts and state legislatures increasingly shape outcomes, as shown by high-profile fights (Indiana’s rejection of a Trump-backed mid-decade map is an example) [8] [9]. Be aware advocacy and partisan actors will promote particular grading outputs that support their policy goals; independent cross-checking between Princeton and PlanScore reduces single-source bias [1] [2].
7. Bottom line
Authoritative grading tools exist — Princeton’s Redistricting Report Card and PlanScore — and they are the right sources to compile letter grades or scores [1] [2]. The provided search results document where extreme maps and litigation have concentrated in 2025 (Texas, Alabama, Indiana among others) but do not supply a pre-built top-20 list with letter grades; to produce one, pull state/map grades directly from Princeton and numeric metrics from PlanScore, then annotate contested maps with Brennan Center or court reporting [1] [2] [4].