The Geometry of Power
Gerrymandering transforms the simple act of drawing lines on a map into a potent political weapon. In this simulation, a grid of voters — colored blue or red — represents a population with fixed preferences. The only variable is how we draw district boundaries. Watch as the same electorate produces completely different election outcomes depending on whether districts are drawn fairly, or strategically packed and cracked to favor one side.
Packing and Cracking
Two techniques drive gerrymandering. Packing concentrates opposition voters into a few districts they win overwhelmingly (say, 90-10), wasting their surplus votes. Cracking splits remaining opposition voters across many districts where they lose narrowly (say, 45-55). The combination means the gerrymandering party wins more districts with fewer total votes — a systematic inversion of democratic proportionality.
The Efficiency Gap
How do we detect gerrymandering mathematically? The efficiency gap, proposed by Stephanopoulos and McGhee, counts 'wasted votes' — votes cast for losing candidates or surplus votes beyond what winners needed. In a fair election, both sides waste roughly equal votes. A large efficiency gap signals that one party's voters are systematically more 'efficient' — the hallmark of gerrymandering. Courts have used this metric in landmark cases like Gill v. Whitford.
Experimenting with Democracy
Use the strategy slider to switch between fair districting, pack-blue, and pack-red configurations. Notice how a party with 50% of the vote can win anywhere from 0 to all seats depending on district lines. The seats-vote disparity quantifies this gap between popular support and political power. This simulation reveals why redistricting reform — through independent commissions, mathematical fairness criteria, or algorithmic approaches — has become one of the most important issues in democratic governance.