Redistricting determines who votes with whom for Congress, shaping representation and party power. Because mapmakers can manipulate boundaries, the Supreme Court has become a key arena for challenging unfair districting under equal protection.

Core concepts: redistricting, unequal representation, and gerrymandering

Redistricting and the problem of unequal representation

In principle, redistricting aims to keep districts roughly equal in population so each person’s vote has similar weight. When districts have very different populations, unequal representation results because some voters effectively have more influence than others.

This concern connects directly to the syllabus emphasis: the Supreme Court has partly addressed unequal representation by allowing equal protection-based challenges to districting.

Gerrymandering as intentional manipulation

Gerrymandering can be pursued through common strategies:

• Packing: concentrating a group’s voters into a few districts to reduce their influence elsewhere

• Cracking: splitting a group’s voters across many districts so they cannot form a majority

Because House elections are district-based, gerrymandering can convert relatively small vote advantages into large seat advantages, affecting polarization, competition, and whose interests are prioritised in Congress.

This diagram holds the statewide voter distribution constant and then redraws three different district maps to show how the same electorate can yield different seat outcomes. It visually demonstrates the central mechanism of gerrymandering: district boundaries, not just vote totals, determine how votes translate into representation. Use it to connect “packing/cracking” logic to real seat conversion effects. Source

Constitutional and judicial foundations (Equal Protection)

“One person, one vote” and apportionment equality

The Supreme Court’s major contribution has been recognising that extreme population disparities in districts raise constitutional issues under the Equal Protection Clause of the Fourteenth Amendment. Key outcomes of these rulings include:

• Federal courts became a venue for reviewing district maps that diluted votes through population imbalance.

• States were pushed toward near-equal population congressional districts, reducing malapportionment-driven unequal representation.

Cases commonly tied to this development include Baker v. Carr (1962) (opening the door to federal court involvement in redistricting) and Wesberry v. Sanders (1964) (reinforcing equal population standards for congressional districts). Together, they illustrate how Supreme Court decisions enabled equal protection challenges to certain redistricting practices.

Limits of judicial solutions

While the Court has addressed some forms of unfairness, not all districting disputes are equally manageable for courts. In particular:

• Racial gerrymandering claims often use equal protection reasoning, scrutinising whether race was the predominant factor without sufficient justification.

• Partisan gerrymandering has been harder to police consistently, meaning some map advantages may persist even after judicial involvement.

These panels illustrate the two classic partisan-gerrymandering tactics—cracking and packing—and then show how the “efficiency gap” counts wasted votes to quantify partisan advantage. The sequence helps students see why partisan gerrymandering disputes often hinge on measurement and legal standards, not just whether a map “looks unfair.” It’s a useful bridge from conceptual definitions to how litigation and expert testimony evaluate maps. Source

Political incentives and consequences in congressional politics

Who draws maps and why it matters

In many states, redistricting is controlled by elected officials, creating a conflict of interest: legislators can influence the boundaries of the very districts that elect them. As a result, maps may be designed to:

• protect incumbents

• secure party advantage

• shape the composition of the state’s House delegation for a decade

Effects on elections and representation

Redistricting and gerrymandering can reshape congressional politics by:

• reducing the number of competitive districts (more “safe seats”)

• encouraging candidates to focus on primary voters, potentially increasing ideological extremity

• altering descriptive and substantive representation by changing which communities are grouped together

Even with Supreme Court intervention against unequal representation, the map-drawing process remains a powerful lever in American elections, and litigation is often a central tool for challenging contested plans.