History
Gerrymandering and Its Effects on Electoral Fairness
Quick fact
The efficiency gap, a metric for partisan gerrymandering, measures wasted votes—votes for losing candidates and votes beyond what the winner needs. A gap of just 2 seats in a 100-seat legislature can persist without flipping, meaning a party can lose the popular vote yet keep a majority.
Why this is interesting
How can a party win fewer votes yet still control the government? The answer lies not in the ballot box, but in the drawing of district lines.
Read the full explanation
Understanding Gerrymandering and Its Effects on Electoral Fairness
Imagine you and a friend each have a bag of colored candies—say red and blue—and you want to divide a flat sheet of cookies into pieces. If you decide where to cut, you can ensure that most pieces contain more of your color, even if your color is overall fewer. Gerrymandering does the same with voters. Politicians draw district boundaries to concentrate or dilute opposition votes. There are two main tactics: 'packing' puts many opposing voters into one district so they win overwhelmingly, wasting their votes elsewhere, and 'cracking' spreads the opposition so thin that they lose many districts by narrow margins. This manipulation doesn't change the total number of votes for each party—it changes how those votes are distributed geographically.
A deeper explanation
The mechanism relies on the winner-take-all nature of single-member districts. Each district elects one representative, and the party with the most votes in that district wins the seat. So the only thing that matters is where the lines fall. By cracking and packing, a party can maximize the number of districts it wins with just over 50% of the vote, while concentrating opponent votes in a few super-majority districts. This creates a disconnect between the statewide popular vote and seat share—a central element of electoral unfairness. The Supreme Court has historically avoided ruling on partisan gerrymandering, declaring it a political question, but has allowed challenges on racial discrimination. The efficiency gap is one attempt to quantify the unfairness, but there is no single agreed-upon measure. Understanding this mechanism is crucial for evaluating electoral systems and reforms like independent redistricting commissions.