Redistricting

A traditional focus for political geographers, particularly those interested in U.S. politics, is redistricting—the process of changing the boundaries of electoral districts to maintain equal populations. It is a critical part of the maintenance of constituency-based systems, particularly those with single-member districts. In international contexts, redistricting is often called boundary delimitation, and in Commonwealth countries, it is called redistribution. In the United States, the term is sometimes used interchangeably with reapportionment, although the latter word more precisely refers to the redistribution of congressional seats among states following the decennial census. Manipulation of redistricting for electoral advantage is called gerrymandering.

Interest in redistricting stems from the fact that the way district boundaries are drawn can have a far-reaching impact on the distribution of political power. Placing large numbers of one group of voters in a single district (packing) or spreading them out over many districts (cracking) are just two of the strategies used by map drawers intent on tilting the balance in favor of one side or the other. Redistricting contributes to the levels of bias and responsiveness in single-member district systems. Bias, the degree to which the ratio of votes cast to seats won varies from 1:1, can undermine the basic fairness of an electoral system. The responsiveness of district-based systems, or their ability to translate temporal changes in voter preferences to changes in the distribution of seats, is constrained by the creation of safe districts and enhanced by competitive ones. The creation of safe districts—a usual result of gerrymandering—is often blamed in the United States for contributing to the polarization of the two main parties, as the party primarily becomes the key contestant and appeal to independents and crossover voters is devalued.