History
Gerrymandering and Its Effect on Representation
Quick fact
In 2012, Republicans won 49% of the popular vote for U.S. House seats but captured 54% of seats, largely due to favorable district maps drawn after the 2010 census.
Why this is interesting
Did you know that who wins an election can be decided before you vote—by how the map is drawn? A cleverly drawn district can turn a 60% majority into a minority of seats.
Read the full explanation
Understanding Gerrymandering and Its Effect on Representation
Think of an election as a recipe. Each district is a bowl. The rules say each bowl produces one winner—the party with the most votes in that bowl. Gerrymandering is the art of arranging the ingredients (voters) among the bowls to favor one recipe. The key techniques are 'cracking' and 'packing.' Cracking spreads a group's supporters thinly across many districts, so they can't win a majority anywhere. Packing concentrates them into one or a few districts, where they win by huge margins but waste votes. Done cleverly, a party can win more seats than its total vote share suggests. This is why some districts have bizarre, ribbon-like shapes—they are crafted to include or exclude specific neighborhoods to achieve the desired math.
A deeper explanation
The mechanism is simple: elections in single-member districts are won by plurality. A party's seat count depends not only on its total vote share but on how efficiently those votes are distributed. If a party 'wastes' many votes in landslides or loses close races, its seat share drops. Gerrymandering exploits this. For example, if Party A has 100 supporters and Party B has 50, and there are two districts, a fair map might give Party A both seats. But a gerrymandered map might split the 100 Party A supporters evenly across two districts, so Party B wins both with 50 votes in each district—even though Party A has twice as many total votes. So the effect is to flip which party gets representation. This subverts the core principle of representative democracy: that the composition of the legislature reflects the will of the people. It also entrenches incumbents and reduces electoral competition. Courts have struggled to define a test for 'too partisan,' but the fundamental issue is that district boundaries are political choices, not neutral lines.