Voting Districts and Redistricting

Every ten years a national census counts the population, and reapportionment moves a fixed number of legislative seats between states based on who grew and who shrank. A fast-growing state gains a seat, a slow-growing or shrinking one loses a seat. No district lines change yet. That comes next, in redistricting: the state with a new seat count must redraw its internal district boundaries so each district holds roughly equal population. Redistricting happens inside a state, after reapportionment has already set how many districts that state gets.

The lines matter because the same voters, grouped differently, can produce completely different winners. Packing one party's supporters into a few districts, or cracking them thinly across many, changes outcomes without changing a single vote. This manipulation, drawn to favor whoever controls the process, is gerrymandering. Because state legislatures often control redistricting, and the party in power at census time draws maps that help itself, the process is easy to tilt.

This is why some states hand redistricting to an independent commission instead of the legislature. Commission members usually cannot hold current elected office, so they have no personal stake in which party wins the next election. Maps drawn this way tend to follow more neutral rules, like keeping districts compact and respecting existing community boundaries, rather than maximizing one party's seats. The tradeoff is political: legislators give up a tool they have used for generations to protect their own power.