How algorithmic redistricting works

Researchers found that 2020 redistricting tactics created safer districts and reduced competition

Studies of the 2020 redistricting cycle show that map-drawing strategies locked in predictable outcomes. The result was fewer competitive races, more incumbents shielded from challengers, and representatives less responsive to broader voter preferences.

Test your gerrymandering skills with this interactive game

This simulation demonstrates how packing and cracking alter election outcomes. See how shifting district lines can change representation—regardless of the overall makeup of the electorate.

Independent redistricting commissions aim to take politics out of the map-drawing process

In several states, citizen or bipartisan panels draw congressional and legislative districts based on neutral criteria like population and geography. Learn more about how these commissions increase competitiveness in elections.

Hear how gerrymandering is like 'Moneyball applied to politics'

In a 2016 interview, journalist David Daley explained how Republicans used data-driven targeting after the 2010 census to lock in durable advantages, comparing modern gerrymandering strategies to the analytics revolution in baseball.

Track the unusual push for mid-decade redistricting across the US

The National Conference of State Legislatures maintains a live tracker showing where mid-decade congressional redistricting is underway, detailing which states are pursuing new maps, the legislative and constitutional methods being used, and how courts are responding as the 2026 elections approach.

In 2025, Democratic-led states moved to counter with their own redistricting plans

In response to Republican mid-decade redistricting efforts, Democratic leaders in California, New York, Illinois, and Maryland signaled plans to revisit their own congressional maps.

Redistricting reshapes political boundaries, usually once a decade after the census

Every 10 years, states redraw congressional and legislative districts based on census data to ensure equal population. Legislatures usually control the process, though some states use independent commissions to curb partisan influence.

See the most oddly gerrymandered districts in the US

Based on input from redistricting experts and political scientists, this resource identifies and ranks the most extreme congressional gerrymanders of the 2020s, examining how map design, cracking, and packing reduce competition and distort representation across states.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Cracking and packing are gerrymandering techniques. Cracking splits opposing voters across districts, diluting their power. Packing concentrates their votes into a few districts, wasting them in overwhelming majorities for one party.

Can courts end partisan gerrymandering?

This podcast explored whether courts can rein in partisan map-drawing, focusing on North Carolina's 2023 redistricting battle, the Moore v. Harper case, and the controversial "independent state legislature" theory.

Mid-decade redistricting is historically rare in modern US history

States have generally redrawn districts only once per decade following the census, with mid-decade redistricting occurring infrequently and usually prompted by court orders or unusual political circumstances.

A 2013 Supreme Court case weakened federal oversight of redistricting

In Shelby County v. Holder, the Supreme Court struck down the Voting Rights Act's preclearance formula, reducing federal oversight of voting laws—including redistricting—and allowing changes to take effect without prior approval.

Experts predict Republicans will gain seats from mid-decade redistricting in 2026

Analysts expect GOP-led states to net seats through mid-decade redistricting, while Democratic states face greater hurdles due to commissions and legal limits—tilting the likely outcome toward Republican gains in 2026.

Republicans launched a mid-decade redistricting push in 2025

Beginning in Texas, Republican-controlled legislatures in Missouri, Florida, Ohio, and North Carolina moved to redraw maps before 2030—an uncommon mid-decade effort aimed at securing additional congressional seats.

Red and blue election maps are a modern media invention

The red–blue color scheme used on election night maps emerged in the 20th century as television networks adopted color graphics to make results easier to follow. The association of red with Republicans and blue with Democrats later became standardized.

States are constitutionally mandated to draw their own congressional districts

Under Article I, Section 4 of the US Constitution, state legislatures possess the authority to determine how congressional districts are drawn. However, Congress retains the power to alter these rules if it chooses to.

Thousands of state voting changes have been federally blocked since the Voting Rights Act

Since 1965, federal oversight has blocked thousands of state-level voting changes—including redistricting plans—by requiring approval for measures that could affect minority representation, a process scaled back by the Supreme Court in 2013.

This American Life explored Ohio's gerrymandering battle

In 2022, Ohio lawmakers repeatedly drew congressional districts that the state Supreme Court ruled unconstitutional. This defiance violated a voter-approved reform intended to prohibit partisan gerrymandering.

Each state’s Electoral College votes mirror its representation in Congress

This overview explains how states receive electors equal to their senators and representatives, and details the legal framework governing how the Electoral College functions during presidential elections.

Federal juries are selected from voter rolls and driver's license lists

Courts randomly draw prospective jurors from these sources, then mail qualification questionnaires. Those who qualify may be summoned for voir dire, where judges and attorneys question candidates before seating a final jury.

Critics say that the Electoral College is outdated and favors small states

This article argues that the Electoral College no longer reflects modern democratic norms, disproportionately advantages smaller states, and warrants broader reform and national debate. (Some readers may experience a paywall.)

Bias can manifest in algorithmic decisions because the program follows rules that may have been written by individuals unaware of their own biases.

There were fewer competitive districts in 2022 than at any point since 1970

Analysts reported that the 2022 midterms featured the lowest share of competitive congressional districts since 1970, reflecting how modern redistricting has increasingly produced safe seats and reduced voter choice.

Thomas Hofeller was the GOP strategist known as the 'master of gerrymandering'

Republican consultant Thomas Hofeller quietly shaped US politics for decades by engineering partisan maps nationwide. His files, released after his death, revealed strategies to maximize GOP advantage and diminish Democratic influence.

The census reshapes House representation every 10 years

Conducted once every 10 years, the US Census determines how House seats are reapportioned among the states. The 2020 results shifted representation as state population growth and decline altered the geographic balance of political power.

A breakdown of algorithms, how they are constructed, and their applications

Algorithms are instructions for accomplishing a goal and typically take the form of a step-by-step procedure. Given the conditions, these procedures can take various paths, increasing an algorithm's complexity. While traditional computer algorithms are programmed to account for all possible scenarios within a given process, machine learning systems build their own rules from data-driven patterns.

The term 'gerrymander' dates back to a 1812 Boston dinner party

The term "gerrymandering" arose when Massachusetts Governor Elbridge Gerry approved a state senate map with a district so contorted it resembled a salamander. Critics dubbed it the "Gerry-mander," cementing the term for partisan map manipulation.

Nate Silver argues the Electoral College can reduce the impact of excess votes

In this article, Silver weighs the Electoral College's flaws—especially popular-vote inversions—against its advantages, arguing it can limit the effect of surplus votes in heavily one-sided states and encourage broader competition.

How the number 15 solved a longstanding math challenge

The “packing coloring” problem asks how many numbers are needed to fill an infinite grid so that identical numbers never get too close to one another. A new computer-assisted proof finds a surprisingly straightforward answer—only 15. While...

How political campaigns use your data

What do campaigns know about US voters, and how do they use that information to shape their strategies during elections? US political campaigns base their strategies and tactics on data collected from more than 200 million voting-age Americans. This visualization by Reuters breaks down how data firms create national databases of voter files, collecting information from a variety of sources to create detailed voter profiles and how political campaigns use that data.

Ranked-choice voting redistributes ballots until a candidate wins a majority

In ranked-choice voting, voters rank candidates in order of preference. If no one wins a majority, the lowest-ranked candidate is eliminated, and their votes are reassigned until a candidate surpasses 50%, avoiding separate runoff elections.

An overview of 12 fundamental types of algorithms and the uses for each

These include search algorithms to quickly process and find important information, cryptographic algorithms to secure communications, randomized algorithms—such as Monte Carlo simulations for estimating probabilities of outcomes—and greedy algorithms, which make optimal choices based on available data in a step-by-step fashion, as seen in navigation apps.

How the Electoral College actually works

In settling on the rules for how the US elects presidents, the Founding Fathers coalesced around a system built on two inputs: Votes from individual voters, and the accumulation of votes from specially chosen Electors. The latter comprise the US Electoral College, and this Washington Post article explains why it exists, how it works, and how its 538 electors collectively decide presidential elections.

Listen to scholars debate abolishing the Electoral College

In this 2016 podcast episode, Harvard's Alex Keyssar and UVA's James Ceaser debate why the Electoral College was created, how parties reshaped it, and what reforms—national popular vote, runoffs, district allocation—could replace it.

How partisan is your district?

The highly-respected Cook Political Report rates how partisan--and therefore, how safe--every district in the US is. Hover over your home district to see the score.

Breaking down the House races

All 435 voting seats in the US House are up for election, but less than 10% of them are competitive. See a breakdown of the races and which way they are leaning here.

Visualize how data becomes organized through a variety of sorting algorithms

This interactive shows how different algorithms shift elements in a randomized set to order them from smallest to largest. By comparing the different procedures and their corresponding functions, users can explore how runtimes vary across algorithms that complete the same task.

An AI-built pixel map reimagines New York City as a video game

Isometric NYC is a zoomable pixel-art map that renders the city in game-style perspective (think SimCity), helpfully clarifying the dense geography and architecture. The makers built the project tile-by-tile using satellite data and generative AI. Zoom into building-level views or out to see all five boroughs.

Explore state-level data on juries.

Algorithms can be designed to train themselves and self-improve without human input, to the point where the optimized code is too complex for programmers to understand.

Breaking down the gubernatorial races

Thirty-six states are holding gubernatorial races this November. Here's a breakdown of which states are holding elections, who is running, and which way the race is leaning.

There’s an artificial intelligence model trained on bankruptcy law

Although it's designed for lawyers, the tool is able to help everyday browsers synthesize important cases and point users to relevant documents about them. One sample using it asks Chatlaw to explain the significance of a recent case and then to define relevant terminology.

Explore jury nullification, the little-known power that lets jurors ignore the law and acquit anyway

When jurors disagree with a law, they can simply vote to acquit regardless of the evidence; however, this practice is rare, and the legal system actively discourages it. This podcast traces its history from a Quaker prayer meeting in London to the LA riots.

A Mississippi man was tried six times for the same crime, each time before an all-white or nearly all-white jury

This podcast investigates how prosecutor Doug Evans systematically struck Black jurors across decades of cases. The team built a database of every jury strike Evans made over 20 years, uncovering a racial pattern that was later cited by the Supreme Court when it overturned Curtis Flowers' conviction in 2019.

What is the Electoral College?

US presidential elections are not “majority rules” contests. A complex mechanism underpins them, guided by the Electoral College system established by the Constitution. This US government website offers an overview of that system, which apportions “electors” for each state and requires winning presidential candidates to secure at least 270 Electoral votes on election night.

Supporters argue that the Electoral College strengthens federalism and election stability

Defenders of the Electoral College argue it preserves federalism, forces candidates to build broad national coalitions, magnifies victory margins to reduce recount disputes, and limits incentives for voter fraud by containing the impact of contested ballots within individual states.

Election 101 podcast

What’s actually at stake when someone casts their vote in a US election? CNN’s “Election 101” podcast series provides ten episodes summarizing some of the basics of democratic elections. The ins and outs of voting are highlighted in 15-minute episodes on voter registration and voting by mail. Additional segments highlight how the electoral system works, how ballots are counted, the Electoral College, why it takes so long to get election results, and more.

Guess US city populations via bracket-style game

The US Census Bureau's data visualization team created a game—laid out like a March Madness basketball bracket—where you try to decide which metro area of two has the greater population. Test your knowledge of relative city populations and see...

Smart pricing algorithms can unintentionally work together to raise prices

Researchers have found that, through trial and error, algorithms designed to adjust prices based on market data can learn to mimic price-fixing tactics, even without explicit programming to do so. Over time, they "learn" that it is more profitable to avoid price wars and keep prices high when competitors lower prices.

Visualize every time Congress has mentioned the word 'democracy' since 1880, and why

This Pudding interactive analyzes every mention of "democracy" in the Congressional Record over 145 years, charting how the word shifted from a partisan label to a concept, and tracking when lawmakers warned the system itself was under threat.