What Gerrymandering Is

Gerrymandering is the manipulation of electoral district boundaries to give one political party or group an advantage, or to weaken the voting power of another. It is distinct from redistricting, which is the ordinary and legally required process of redrawing district lines. Understanding gerrymandering means understanding both how districts are normally drawn and how that drawing can be bent to shape election outcomes. This explainer describes the practice neutrally, without endorsing any party or position.

How is gerrymandering different from redistricting?

In systems that elect representatives from geographic districts, boundaries must be redrawn periodically, typically after a census, so that each district holds roughly the same number of people. This redrawing is called redistricting, and it is a normal, required part of representative government. Gerrymandering is not the act of redrawing itself, but the deliberate shaping of those lines to favour one side. Put simply, redistricting is the process, and gerrymandering is the manipulation of that process. The same task, drawing a map, can be carried out fairly or abused, which is why the two terms are often confused.

How does gerrymandering work?

Because election results depend on how voters are grouped, whoever controls the map can influence outcomes without changing a single vote. Britannica and other reference works describe two primary techniques.

Technique	What it does	Effect
Packing	Concentrates a group’s supporters into one district	Wins that district by a wide margin, wasting extra votes and reducing the group’s influence elsewhere
Cracking	Splits a group’s supporters across many districts	Prevents the group from forming a majority in any single district

By combining packing and cracking, map-drawers can help one side win more seats than its overall share of votes might otherwise suggest. The result is often districts with unusual, sprawling shapes, because the boundaries follow patterns of voters rather than natural or community lines.

Where does the term come from?

The word dates to 1812 in the United States. Elbridge Gerry was then governor of Massachusetts, and a law signed during his term created district boundaries seen as benefiting his party. One district was said to resemble a salamander in shape. A newspaper combined Gerry’s surname with salamander to produce gerrymander, and the term has been used to describe the practice ever since. The origin explains both the word and the enduring image of oddly shaped districts.

What are the different kinds of gerrymandering?

Analysts commonly distinguish two broad categories. Partisan gerrymandering is drawing lines to favour a political party. Racial gerrymandering involves drawing lines in a way that dilutes, or in some contexts protects, the voting power of racial or ethnic groups. The legal treatment of these categories differs significantly, which is central to how the practice is regulated.

What has the law said about gerrymandering?

Legal responses vary by country and, within the United States, by whether a claim is partisan or racial. In the 2019 case Rucho v. Common Cause, the US Supreme Court ruled five to four that partisan gerrymandering claims present political questions that federal courts lack the authority to decide. Chief Justice John Roberts, writing for the majority, acknowledged that extreme partisan gerrymandering can be at odds with democratic principles, but concluded there were no clear, manageable legal standards for federal courts to apply. The dissent, led by Justice Elena Kagan, argued the courts could and should act. Importantly, the ruling left open other avenues: state courts may still address partisan maps under state constitutions, and racial gerrymandering claims can still be brought in federal and state courts. This explainer presents the decision as a matter of legal fact rather than taking a side on it.

Why does gerrymandering matter?

Because districts determine which voters are grouped together, the way lines are drawn can affect how competitive elections are and how closely the makeup of a legislature reflects the overall vote. Supporters of stricter limits argue that heavily skewed maps can reduce competition and weaken accountability. Others contend that some degree of political judgement in map-drawing is unavoidable and that elected bodies are the appropriate place to make such decisions. Both perspectives are part of an ongoing public debate.

How do jurisdictions try to limit it?

Approaches differ and no single method is universal. Some places assign redistricting to independent or bipartisan commissions rather than to the legislature. Others rely on court challenges, particularly under state constitutions, or set rules requiring districts to be compact, contiguous and respectful of existing community boundaries. Researchers have also developed mathematical tests to flag maps that appear unusually skewed. Each approach has trade-offs, and their availability depends on local law.

How is gerrymandering measured?

Because oddly shaped districts do not always prove intent, analysts have looked for ways to gauge how skewed a map is. One common idea is the concept of wasted votes, meaning votes cast for a losing candidate or beyond the number needed to win. Some proposed measures, such as the efficiency gap, try to compare wasted votes between parties to estimate an advantage. Others examine how compact districts are, or use computer simulations to generate large numbers of alternative maps and see whether an actual map is an outlier. These tools can inform debate, but in Rucho v. Common Cause the Supreme Court majority concluded that no such standard gave federal courts a clear, manageable rule to apply. Measurement therefore remains a subject of ongoing academic and legal discussion rather than a settled test.

Does gerrymandering only happen in the United States?

The word originated in the United States, and much of the best-known debate takes place there, but the underlying issue of who draws electoral boundaries and how arises in many countries that elect representatives from geographic districts. Different systems address it in different ways. Some place map-drawing with independent boundary commissions by law, while others leave more discretion to elected officials. Comparing systems is complex, because rules, institutions and political contexts vary widely, and this explainer does not evaluate which arrangements are best. The general point is that the tension between routine redistricting and its potential manipulation is not unique to any single country, even if the terminology, institutions and legal remedies used to address it differ from place to place.

The bottom line

Gerrymandering is the manipulation of electoral boundaries for advantage, distinct from the routine redistricting that all district-based systems require. It relies chiefly on packing and cracking voters, it takes its name from an 1812 episode in Massachusetts, and its legal status depends on whether a claim is partisan or racial. It remains a subject of active legal and public debate, with reforms ranging from independent commissions to court oversight, and no consensus on a single solution.

Sources

• Encyclopaedia Britannica — Gerrymandering
• Supreme Court of the United States — Rucho v. Common Cause opinion
• Congressional Research Service — Partisan gerrymandering (Legal Sidebar)
• Brennan Center for Justice — Gerrymandering explained

Related from Politics