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Why the Post-Redistricting, Pre-Primaries Work Matters

It is the job of state and local election officials to prepare for every election, but the election that follows redistricting has more change (and therefore more work) than others throughout the decade. The first elections are likely to be the primaries held in the year ending in “2.” In 2022, the first primary is scheduled for March 1, in Texas.

Accuracy in elections starts well before Election Day, especially when new electoral districts for Congress and state legislative chambers are handed off from the state’s entity that is responsible for redistricting (mostly state legislatures but sometimes a redistricting commission) to election officials. Accurate information about each electoral district—congressional, legislative, local and special districts—must be determined so each voter is accurately assigned to the appropriate districts.

As districts are being finalized, election officials are also checking the physical address for each voter. It’s from this address that the voter’s ballot is determined: which contests (state, federal and local) and ballot measures are they entitled to vote on? It’s a matter of geography.

In fact, it is the overlaying of these two kinds of data—electoral districts’ boundaries and voters’ residential location—that must be completed before new elections can be held based on those new maps. And this work is step one in ensuring election accuracy.

“The fewer the errors in election administration, the greater public confidence in the integrity of elections,” according to the Local Election Officials’ Guide to Redistricting, from the U.S. Election Assistance Commission. Those errors can be reduced with attention to the details that start long before Election Day.

Even though newly redistricted congressional and legislative maps are expected to be final for the next 10 years, other district boundaries will change throughout the decade as municipalities grow, developments are added, rivers change course and highways are built, for instance. And of course, voters move in and out of jurisdictions. It is not possible to ever align all boundaries and voter data—but it is the aim.

The core way that is done is by assigning voters to precincts (also known as wards), which are the building blocks of electoral districts. Unfortunately, it is easy to make mistakes; some say that 12 percent of voters are placed in the wrong district, based on unpublished reviews of manually-maintained voter lists. “As more states and counties are using GIS for election purposes, we can expect the error rate—whatever it might be—to go down,” said Richard Leadbeater, of Esri.

Sometimes, errors have consequences. For instance:

  • In the 2017 legislative elections in Virginia, an extremely tight race for state delegate came down to a tie, with the winner being chosen by picking a name out of a bowl. The result determined not just who would be sworn in, but also which party would control the Virginia House of Delegates. It turns out that some voters in this district were misassigned, and it will never be known how the race would have turned out if only the right voters had been able to vote in this race.  See this Washington Post article for more.
  • In Franklin County, Ohio, 2,000 residents received ballots with the wrong congressional race on it for the 2018 election, because of confusion about a district boundary, which led to 56 votes being wrongly cast in a special election primary.
  • Poorly identified and publicized districts can have consequences for candidates as well. In 2011, Deseret News released an article detailing a longstanding mix-up between county maps and state district maps which led to a representative inadvertently running in the wrong district. (Since then Utah has become a leader among states in using GIS for election administration as well as redistricting.)
  • In 2019, a Greenville, N.C., a city council candidate learned at the polling booth he did not live in the district he was running to represent. He had successfully filed to run in Greenville’s District 2, but an audit conducted by the Pitt County Board of Elections after the filing period found that he actually lived in District 1. The street had been coded incorrectly for 20 years.

Local Redistricting

All levels of government that elect representatives from geographically-defined districts, and in which only voters from those districts may vote, must redistrict periodically. Federal law is clear that states must redistrict every decade after the decennial census. It is less clear on when, or how often, local redistricting must take place. In places that use at-large elections to fill local commissions, redistricting is not necessary. Population growth or annexations can trigger municipalities, school districts, fire districts, or other special districts to redraw their districts.

Still, if a county or other local jurisdiction does not redistrict occasionally, it can be sued based on the one-person, one-vote principle.

California’s law requires counties to redistrict and specifies the criteria to be used. Additional sections of California statute apply to cities, schools and special districts.

States with caps on population or other criteria would have those requirements. Arizona caps the Justices of the Peace/Constables district size as a way to monitor court workloads for example.

In Indiana, after the 2011 congressional and legislative redistricting process was over, very few county councils followed suit, according to a study from DePauw University. The same is likely true across the nation.

These local entities may have other reasons to change their boundaries or their names and any of these changes must be captured by election officials in their election management systems. If the local election office has access to GIS, it is better equipped to help local entities undertake local redistricting.

A schedule for local redistricting could be established by statute. In Minnesota, local redistricting begins when new precinct boundaries are set (Minn. Stat. Ann. § 204B.14 (3)); and ends 20 days later (Minn. Stat. Ann. § 204B.135 (2)). The full Minnesota list of key dates and laws that impact redistricting for local governments is here.

How each entity conducts its local redistricting varies. In California, some counties have their own independent redistricting commissions. In other California counties, local election officials make maps for approval by the governing body of the jurisdiction in question or assist the governing body with that work. Other states vary too, and legal requirements based on state law or local ordinance must be followed. These might pertain to public input, public outreach, and notification requirements.

No matter when local redistricting takes place—immediately following congressional and legislative redistricting or at other times—the same steps relating to district boundaries, precinct boundaries and voter assignment outlined below pertain.

Reviewing and Updating District Boundaries

The entity within the state responsible for redistricting (usually the legislature, occasionally a commission of some sort) provides new congressional and legislative maps to local jurisdictions.

Those maps are brand new, but even so it’s not unheard of for technical fixes to be required when simple definitional errors are made.  Local jurisdictions may be able to point those out. In Maine, for instance, the secretary of state is authorized to “resolve ambiguities concerning the location of election district lines” consistent with a set of standards included in the state law (Me. Rev. Stat. tit. 21-A, § 1207).

From there, election officials make sure all other district boundaries are as clean as can be. School districts, hospital districts, fire districts, etc. can change at any point in the decade, and after redistricting is a likely time to closely review these.

By looking at the many district maps overlayed upon one another, it is not uncommon to find minor discrepancies based on cul-de-sacs, rivers, new highways, etc. Election administrators work with representatives of these other entities to find and fix anomalies. Any time one of these districts is changed, the boundaries for its neighbors must be reviewed as well. This job goes on throughout the decade, but the changes are greatest right after redistricting.

When boundaries can be reviewed with a geographic information system (GIS), errors are more easily spotted and fixed. GIS is not always available at the local level. Washington provided its state-level expertise to assist all local jurisdictions in a recent revamp of elections management.

Some states require that all district maps be submitted to the state, although most do not. In Arkansas, the county clerk is required to submit written, printed and digital copies of the map and boundaries to the secretary of state and Arkansas Geographic Information Systems Office within 30 days of any changes (Ark. Code Ann. § 7-5-101).


Election officials are responsible for “reprecincting,” or moving precinct lines. Precincts, also known as wards in some parts of the country and parishes in Louisiana, can be thought of as the building blocks for all other electoral districts.

State-level redistricters try to adhere to existing precinct lines, but that is not always possible. One way a legislature can address this is to set a cutoff date in statute, after which local jurisdictions are prohibited from making new precinct changes prior to redistricting. New Mexico, for instance, requires all precincts be updated prior to redistricting (N.M. Stat. Ann. § 1-13-12).

Once redistricting is done, election officials can and frequently do change precinct lines to ensure they fit within new congressional and legislative boundaries. As an example, Iowa requires local jurisdictions “shall make any necessary changes in precincts “as soon as possible after the redistricting of congressional and legislative district become law” (Iowa Code § 49.7) and prohibits counties or cities from making additional changes to precincts until after the next decennial census, with some exceptions (Iowa Code § 49.8).

Because one person, one vote doesn’t apply to administrative units like precincts, election officials can determine when splitting a growing precinct is warranted, or when merging two underpopulated districts may make sense. Texas addresses combining precincts when the number of registered voters is less than 500 (Tex. Elec. Code § 42.0051). If district lines from different kinds of districts don’t follow the same path (a street, river, canal, etc.), there may be strips of land that are unaccounted for; the goal is to have “coterminous” lines, and when these situations are found, the lines will need to be redrawn for proper alignment.

Local election officials are likely to draft new precinct maps, which are submitted to the governing body, such as the county commission, for adoption.

States may have laws requiring that:

  • Precincts do not cross district boundaries, at least for some types of districts. It is common to prohibit precincts from overlapping more than one congressional or legislative district, for instance.
    • In California, election results are required to be reported by precinct (Cal. Elec. Cde § 15321), so to do this, and also to report results by municipalities, precinct boundaries can’t cross city boundaries.
    • In Colorado, precincts must not overlap legislative or congressional districts (Colo. Rev. Stat. § 2-2-506).
    • Kentucky also prohibits precincts from overlapping legislative and congressional districts, and adds county lines and other local district lines as well (Ky. Rev. Stat. § 117.055).
  • Precincts do not exceed a certain number of voters; Michigan sets the maximum number for consolidated precincts at 5,000 (Mich. Comp. Laws § 168.659).
  • New precinct maps must be determined a certain time prior to Election Day. In California, precincts can’t be changed within 125 days of the election (Cal. Elec. Code §§ 12262, 10524). In Illinois, the cutoff is 60 days prior to an election (10 Ill. Comp. Stat. Ann. 5/11-1).
  • The state can maintain a continuously updated map of all precincts and can require state-level review of local changes. Kentucky requires both. The Legislative Reference Commission, a nonpartisan organization within the legislature, “shall maintain and continuously update a computerized map of Kentucky containing census geography and election precinct boundaries” (Ky. Rev. Stat. § 7.550) and reviews all proposed precinct establishment orders from the State Board of Elections (Ky. Rev. Stat. § 117.0556).

Like with district boundaries and local redistricting, using GIS can increase accuracy and efficiency in developing precinct maps. Inyo County, Calif., uses a county-wide GIS department to create its precincts. Virginia requires GIS mapping be used for establishing district and precinct boundaries, and if the local jurisdiction doesn’t have that capacity, the state department of elections will do it for them.

Avoiding Split Precincts (And Split Census Blocks)

State redistricters prefer not to split city and counties between congressional or legislative districts, and many times state law requires these and other political subdivisions be kept whole if possible. In the same way and for similar reasons, election officials prefer to avoid “split precincts.” If new congressional and legislative maps do split existing precincts, election officials are likely to redraw the precincts to avoid the inherent problems associated with “splits.”

Examples of those problems:

  • In states where precincts are split between two districts for any reason, the number of ballot styles multiplies, which has a financial cost associated with extra design and printing costs.
  • Split precincts may reduce voter confidence, because neighbors who expect to get the same ballot are now getting ballots that are different for at least one minor race.
  • “Splits” may lead to so few voters getting the exact same ballot that the secrecy of an individual’s ballots may be hard to maintain.

Precincts are made up of even smaller geographic units, called census blocks. Census blocks are defined by the U.S. Census Bureau, and generally, census blocks are kept whole. States can work with the bureau to improve their accuracy through the Block Boundary Suggestion Project, the Local Update of Census Addresses Operation and the Boundary and Annexation Survey.

Some states require local jurisdictions to provide updated precinct maps to the state on a regular basis. Nevada does so, with a requirement that maps be submitted by the end of March in even-numbered years (Nev. Rev. Stat. Ann. § 293.206). California requires that precinct maps be submitted after each general election (Cal. Elec. Code § 17501).

Assigning Voters to the Correct Districts

After all geographic boundaries are aligned as best as possible, the next job is to place voters in the correct precinct. In most cases, it is that precinct that then defines the many electoral districts the voter is in—congressional, legislative, etc. Districts nest within each other, but not always neatly, as is the case when a school district overlaps two municipalities. In some cases, even a single precinct can be "split" and contain multiple electoral districts, particularly for more local offices. Since the creation, maintenance, and naming of precincts and electoral districts happens across varying levels of government, it can be helpful to use a standardized naming schema such as Open Civic Data Division Identifiers in addition to more colloquial names. That way, different systems can know they're both talking about the same "School District 1" or "Western Precinct," should they need to communicate across governmental departments or levels.

Each voter’s address can be thought of as a geographic point, one that could be defined by latitude and longitude; this is similar to how your location can be “pinned” on a Google map or other map app. If GIS is available for use by local election officials, then each voter’s address is assigned a point, which is immediately and automatically assigned to the right precinct. This is called “geocoding,” and states can adopt different strategies to do it. See NSGIC’s Best Practices for Geo-Enabling Elections for more.

Note, too, that Next Generation 911 (aka NextGen 911 or NG911) is being adopted by states and localities to better provide emergency services. Getting NextGen 911 up and running means each residence will be geo-coded. It could be possible for this information to be shared with election officials.

It is all but certain that the state’s redistricting entity has its new maps and data available in a digital format, even if the bill adopting the new maps uses some other system, such as metes and bounds, to identify the plan.

It is less likely that election officials have the capacity to receive the maps geographically and work with them in GIS. In 2021, the Geo-Enabled Elections project—a part of the National States Geographic Information Council (NSGIC)—surveyed state election directors on how their states used geographic information systems to manage elections processes and received 27 responses. Of those, three-fourths indicated their voter registration systems did not support GIS data.

In the many jurisdictions where GIS is not available, voter assignment to precincts is done by hand, based on tabular—not spatial—information about voter addresses. This process leaves room for error.

Some local election offices may simply have maps on a wall, with district and precinct boundaries superimposed on it, possibly with marker on an acetate overlay, although in Shasta County, Calif., the old paper maps are hand-colored with colored pencils at least through the 2010 post-redistricting cycle. A clerk looks at a voter’s address, finds the corresponding precinct, and assigns the voter to that precinct in the voter registration database. This generally works, but, according to Election Data Services, some residences are on borders of precincts, leading to 12% of voters being misassigned. Also, if a voter gets a ballot that doesn’t include the races they expect, that is a problem—and it hurts voter confidence.

Many offices have moved to keeping street segment files in a database to determine what districts a given voter is in. A “street segment” is a range of addresses on a single street where all voters within the range are assigned to the same precinct or district. All addresses within a jurisdiction should be able to be placed within a defined street segment, and an address should never be in more than one segment.  Since precinct or district lines often run through the middle of streets, some voters with similar addresses may be assigned differently depending on the side of the street they live on. Typically, this is represented by adding an “odd”, “even”, or “both” parameter to a street segment.

For jurisdictions with addresses that do not follow normalized naming or numbering conventions, individual address points may be represented as street “segments”, though having a high number of such single-residence points can make lists harder to maintain and more likely to introduce accidental inaccuracies.

A street segment file containing the following segments to assign addresses to precincts:

Start House Number

End House Number

Street Name

Street Suffix

Odd, Even, Both

Precinct ID

1500 2000 7th Avenue Both C
1651 1959 12th Avenue Odd C
453 453 Elm Street Both C
1901 1999 Main Street Odd C
1900 1998 Main Street Even G

Which in turn can be used to place voters into their correctly updated districts as below:



First Name




Old District

New District

3931154 Smith John 7th Avenue 1858 C 1 3
4420947 Adams Samuel 12th Avenue 1659 C 1 3
3342913 Adams Martha Elm Street 453 C 1 3
4301660 Rodriguez Edward Main Street 1901 C 1 3
4404091 McDonald Michael Main Street 1902 G 1 1

Maintaining geographic information in a list format is not wrong, but it can introduce errors because address changes and additions cannot be viewed spatially. For instance, if there is an error in translating geography into a list, it will likely not be identified. And updating street segment files after redistricting (or reprecincting) is laborious—but also necessary for added assurance and transparency. An election management system may manage much of this work, but without an audit (see below) it is hard to find misassignments. New or extended segments may be needed to be regularly created to reflect new construction or changes to land use, even outside of a redistricting cycle, so offices should be prepared to regularly implement these procedures for maintaining and assuring accuracy of assignments between elections.

Still other states may produce their redistricting maps as “block equivalency files,” in which each census block is assigned to congressional, state Senate and state House districts. This is more precise for redistricting purposes since census blocks account for all geography in the nation. When election officials receive data in these files, they can use the same census blocks to create precincts—but it doesn’t solve the need to assign voters’ addresses to the right precinct.

Verifying (or Auditing) Voter Assignments

Throughout the decade, but especially during the post-redistricting phase, election officials double check everything they can.

First, they check for any voters who are not assigned to a precinct or have an incomplete district profile. Then election officials will look for incomplete addresses; incorrect road designations such as “lane” instead of “street;” overly long address ranges in a street segment file; and addresses that appear to be duplicated between two street segments. Experienced election officials know this work is time- consuming—but it is this detailed work that leads to voters getting the correct ballot, which leads to more accurate elections and improved voter confidence.

This can be done by cross-checking voter’s addresses against U.S. Postal Service lists, U.S. Census Bureau address lists, or lists maintained by other parts of local or state government. No list will be perfect, but comparisons can point out inconsistencies for manual review. In the Geo-Enabled Elections survey, “two-thirds of respondents reported not having access to, or not knowing if they had access to, a universal address list such as data from 911 address databases or the National Address Database (NAD).

The comparison can also be done by using GIS. In North Carolina, local election boards submit their precinct maps to the state board of elections (SBE). The SBE periodically uses its GIS capacity to run the state voter registration database against those local maps. The SBE then returns to the local officials a list of anomalies for review and correction, if needed.

A Timeline for Post-Redistricting Work

Election officials plan backwards, starting with the date of the first election where the new districts will be used—generally the primary election in the year ending in “2”.

Ballots must be ready in time to meet the federally mandated mailing date for ballots going to overseas voters: 45 days before Election Day. That requirement was established in the Military and Overseas Voters Empowerment (MOVE) Act of 2009, to ensure overseas voters won’t be disenfranchised because of slow international mail delivery.

The printer needs a week or two to print before that.

Ballot design takes a week or two before printing. “Design” is mostly about determining which races belong on each precinct’s ballot, which candidates have qualified for those races, and any ballot questions that have qualified. Primary elections create twice the number of ballot styles because separate ballots are prepared for each major party, or even more if there are more than two recognized major parties. Many jurisdictions have dozens of distinct ballot designs based on the number of races and precincts; large jurisdictions can have thousands. Split precincts mean even more ballot styles.

Good ballot design also includes attention to usability, literacy level and creating audio ballots for those with visual impairments. The Center for Civic Design provides advice on ballot design.

Candidate filing dates, both the start and end dates, are set by state law. Many start in the first few months of the new year, but some begin in October or even September in the year before the election. The calendar also specifies when signature-gathering can take place for citizens' initiatives and popular referendums; if these are local measures, as opposed to statewide measures, voter eligibility will be part of the equation.

Election officials are also engaged in all the usual election preparation steps:

  • How many polling places will be required?
  • Where are they located, and is the distribution equitable based on demographics?  
  • Are resources such as equipment and supplies in place?
  • How many poll workers will be needed? How will they be recruited and trained?
  • What is the anticipated level of absentee, or mail, voting?
  • What communications to the public will be used, especially to notify voters of changes to their districts and precinct, which often translates into a different polling location?
  • What safety and security procedures will be followed?

The list goes on, and each of these jobs is more complex right after redistricting, and timing is of the essence.

Candidate Filing

Voters are paramount, but candidates are important too. Once districts are finalized, the candidate filing period can begin (and this period can be months before the first election is held with new districts). Election officials are responsible for communicating new district boundaries to candidates and ensuring the candidates are qualified to run and serve in the district they have indicated; is their address indeed inside the district? Worst case scenario:  a candidate files in the wrong district. This is bad for voter confidence as well as for politics.

When lines are in dispute after filing deadlines have passed, states are likely to have a remedial process; it would be common to allow candidates to circulate nominating petitions based on existing boundaries—even though those voters may not be the ones able to vote for the candidate after final lines are adopted.

Fortunately, assigning voters to precincts and checking candidate addresses can be done simultaneously.

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