ABC Tools
Gerrymandering Sandbox illustration

Gerrymandering Sandbox

A state of two-party voters, and you hold the district pen. Paint the map into districts and watch the seat count swing while not a single voter changes their mind — the whole dark art of packing (cramming opponents into a few wasted landslides) and cracking (splitting them thinly across many safe losses) under your own cursor. Set the party split and how strongly voters cluster, then compare your map against automatic plans: compact districts, a pro-A gerrymander and a pro-B gerrymander for the very same electorate. Live scoreboards show seats vs. votes, wasted ballots and the efficiency gap, so you can see exactly how far a map strays from the popular will — and how easy it is to make it stray on purpose.

Runs 100% in your browser — simulations are computed locally on your device.

Read the full guide to this tool

Notes

  • Packing and cracking are the only two tricks there are: waste opponents’ votes in overwhelming wins, or spread them below the winning threshold everywhere else. Every real gerrymander is a mix of the two.
  • The efficiency gap totals each party’s wasted votes (all losing votes plus winning votes beyond 50%) and divides the difference by all votes; plans beyond roughly ±8% have been argued in court to signal intentional gerrymandering.
  • A perfectly proportional outcome is often geographically impossible: when one party’s voters cluster in cities, even neutral compact districts under-represent them — clustering is a "natural gerrymander."
  • Runs 100% in your browser — simulations are computed locally on your device.

Explore the idea

This interactive demo needs JavaScript.

Read the full guide for the explanation behind it

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