Gerrymandering: Packing and Cracking

Whoever controls redistricting controls the map, and the map controls outcomes even when nobody's vote changes. Packing means cramming as many of the opposing party's voters as possible into a small number of districts. Those districts become landslide wins for the opponent, but landslides waste votes: winning a district 95 to 5 uses way more support than winning it 51 to 49. Cracking does the opposite. It splits a concentrated bloc of opposing voters across several districts so that in each one they're outnumbered and lose. Neither trick changes how many people voted which way. Both change who represents them.

Put the two together and a party can turn a minority of votes into a majority of seats. If a state has 100 voters split 60-40, and the 40 percent draws the map, they can spread their 60 opponents thin across many districts while concentrating their own 40 supporters into just enough districts to win most of the seats outright. The party that loses the statewide vote wins the legislature. This is why vote share and seat share can diverge sharply, and why the gap between them is the standard way to measure how much a map favors one side.

This connects directly to who draws the lines and who can challenge them. Legislatures redraw districts after each census, so the party in power after an election often controls the next decade of maps. Courts review maps for racial gerrymandering under the Voting Rights Act and the Constitution, but a district's odd shape by itself proves nothing. Shape can come from rivers, highways, city boundaries, or deliberate efforts to keep a protected minority group together, not just from partisan line-drawing.