Nuts and Bolts of Redistricting

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Redistricting is the process of drawing boundaries for electoral and political districts in the U.S. and is usually done every ten years after the census. The last U.S. census took place in 2020 and all states must adjust their voting districts to align with changes in population. The U.S. Constitution requires each Representative in Congress represent an equal number of citizens and mandates a census to determine the number of citizens and apportion seats to each state.


The U.S. Constitution (in Article I, Section 2) requires that Representatives be apportioned among the several states according to their respective numbers and specifies that there be at least one Representative for every 30,000 citizens (and each state must have at least one Representative). Every ten years, the Census Bureau conducts a nationwide census and informs each state how many seats it will have in the U.S. House of Representatives for the next decade.


Individual states have the responsibility of drawing legislative boundaries for congressional districts as well as for state legislative districts. In most states, the state legislature redistricts seats, usually subject to concurrence by the state governor. A few conduct redistricting through an independent or bipartisan commission in order to minimize the impact of partisan or legislative politics. A handful allow an independent commission to propose redistricting plans subject to approval by the state legislature.

Each state maintains standards for creating electoral districts. Beyond equalizing the population of districts and complying with other federal requirements, criteria may include creating compact, contiguous districts; keeping political units and communities within a single district; and avoiding the drawing of boundaries for purposes of partisan advantage or incumbent protection.


Criteria varies greatly by state. In South Carolina, the League of Women Voters has discussed the issue of who draws legislative district boundaries during the redistricting process. Do voters choose their representatives, or do representatives choose their voters? The criteria for drawing boundaries may be an even more important issue than who draws those boundaries in answering this question in favor of voters. The League recommends an independent advisory committee to consider diverse perspectives during redistricting.

Court cases over the years have established more specific guidelines for how these universal requirements are implemented. Within those boundaries, each house of the SC General Assembly has created its own specific criteria. In 2011 the South Carolina Senate issued its criteria and the House also issued criteria. The House criteria of 2011, interestingly, include “Incumbent Protection” as a specific requirement. The House and the Senate do not need to adopt the same criteria.

We may assume that electing legislators from districts is mandated under the U.S. Constitution, but we’d be wrong. Until 1967, states could and did elect Congressional representatives from combinations of single, at-large and multi-member districts.

The 1965 Voting Rights Act prohibits voting practices and procedures that dilute the ability of minority voters to elect candidates of their choice. In most instances, a single-member district was a remedy to that potential dilution.

In the 60’s, times were a-changing. Several U.S. Supreme Court decisions, led by Baker v. Carr in 1962 and Reynolds v. Sims in 1964, provided for “one person, one vote”. The courts ruled that each district had to contain the same population, which is counted by the census each decade.

As with many well-intentioned regulations, powerful people quickly figured out how to work around the rules. They learned to pack similar voters in the same district or put so few in a district that they would have little to no impact on an election.

In 2021, the Bureau of the Census will release population estimates for the United States. If there is more than a 10% difference in population between the biggest and smallest Congressional district in each state, those districts will be redrawn or redistricted.

We should ensure that redistricting upholds the spirit of the Voting Rights Act. One way to do that is to urge state and local government to have an independent commission draw districts.

Imagine a large table somewhere in a back room of the State House. On it is unrolled a huge map, surrounded by lawmakers, each standing ready to mark their territory. Of course, that’s not how it happens with modern redistricting. These days, it’s more point-and-click than magic markers and sharp elbows.

The mechanics of redistricting involves sophisticated mapping software that allows easy point-and-click district construction. Vendors with names like Caliper and Esri offer dedicated redistricting programs. Open-source (free) software like QGis makes mapping readily available. As the maps are drawn, district statistics are displayed, changing dynamically as the lines move.


Currently, some redistricting software providers sell versions that can be used online, including by citizen map drawers. As artificial Intelligence continues to develop, redistricting will become more automated and rules-driven.

The core Census data file for redistricting includes both total population and voting age population for each layer, including census blocks, precincts, cities and towns, and counties. Mappers may also easily add other data from the Census, IPums, SC Election Commission and data vendors, allowing narrow targeting.

Historically, the Census data has provided detailed racial and ethnic breakouts, but has not recently included citizenship. That may change in 2020. The measure of one person, one vote in South Carolina comes down to how many people are found and willing to be counted in the Census. That number will be used for all redistricting until the next Census, in 2030.


gerrymandering (present participle)

  1. manipulate the boundaries of (an electoral constituency) so as to favor one party or class.
    synonyms: manipulate · arrange fraudulently · interfere with · influence · juggle · massage · distort · misrepresent · pervert · maneuver · tamper with · tinker with · doctor · falsify · forge · fake · engineer · trump up · fix · cook · fiddle

  2. achieve (a result) by manipulating the boundaries of an electoral constituency.
    “a total freedom to gerrymander the results they want”

Gerrymandering is a practice intended to establish an unfair political advantage for a particular party or group by manipulating district boundaries, which is most commonly used in first-past-the-post electoral systems. Two principal tactics are used in gerrymandering: “cracking” (i.e. diluting the voting power of the opposing party’s supporters across many districts) and “packing” (concentrating the opposing party’s voting power in one district to reduce their voting power in other districts).

Learn more about each element that impacts gerrymandering:

  1. Gerrymandering?

  2. Types of Gerrymandering

  3. VRA

  4. Limits

  5. History

  6. Partisanship

  7. Bridging the Gap

One of the hallmarks of a racial and partisan gerrymandering is the existence of unusual or bizarre-looking districts. The Colleton Court in the 2001 statewide redistricting litigation declared that traditional South Carolina districting principles required that “districts should be as compact as reasonably possible” (at 647).

Judges across the nation have ruled districts not reasonably compact. “Some characteristics of districts people view as noncompact are wiggles, arms, noncontiguous segments, river-like features, or being much longer than wide.” (Kaufman et al., 2019, Suppl. Appdx., at 6-7.) A number of Congressional districts have been singled out as particularly ugly—none in South Carolina. Some, like Pennsylvania’s old 7th District or North Carolina’s old 1st District no longer exist due to judicial intervention. Yet, the Illinois 4th District remains after several challenges.

Social scientists and mathematicians have developed test after test of compactness. The same district can do well in one test and poorly in another. The current 6th or 1st Congressional District may be the least compact South Carolina Congressional district.

The courts have not adopted any of the tests. Judges generally rely on eye-ball tests. If it doesn’t look compact, it’s not compact. A forthcoming study by Kaufman et al. says judges and politicians basically get to the same place as the social scientists and mathematicians.

When redistricting begins in 2021, South Carolina – along with the other 49 states – will draw new legislative districts for the U.S. House and the state legislature. Redistricting is legally required every 10 years.

South Carolinians may be surprised to learn that neither the South Carolina Constitution nor state law provides any criteria for constitutional districting. But in 2002, as part of statewide redistricting litigation, the Colleton Court (at 646-648) outlined traditional districting principles for The Palmetto State:

  • Maintain the cores of existing districts
  • Draw districts as “compact as reasonably possible”
  • Draw contiguous districts
  • Respect county and municipal boundaries
  • Preserve communities of interest
  • Don’t draw incumbents out of their districts

The South Carolina Senate and the House adopted separate redistricting criteria in 2011 that largely followed the Colleton Court’s outline. Unless guided by law changes, they will almost certainly do so again in after the 2020 census.

South Carolina and all states must be in compliance, of course, with the U.S. Constitution and the Voting Rights Act. State constitutions, laws, or legislatively-adopted criteria may set districting criteria, too. In addition, Courts look to “traditional districting principles.”

Interestingly, in some states, criteria not only differ but may be contradictory. Some states, for example, allow partisan advantage as a criterion; others prohibit it. Some states allow incumbency protection; others prohibit it. Wisconsin even allows non-contiguous districts.

In the end, however, except for the requirements imposed by the U.S. Constitution and the Voting Rights Act, districting criteria are policy choices. Policy choices made in other states or under consideration could offer guidance to changing how South Carolina draws electoral districts.

John C. Ruoff, Ph.D.
The Ruoff Group

Dr. John Ruoff has been involved in redistricting since the mid-1980s. He has drawn and evaluated maps for every level of single-member districts in South Carolina, from boards of public works to the U.S. Congress, including the last three rounds of statewide redistricting. He has testified and consulted as an expert in redistricting and Voting Rights court cases.

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