Who Draws the Lines – Congressional Redistricting

January 19, 2022

The once-a-decade battle to redraw the U.S. political map is underway based on findings from the 2020 Census – a constitutionally mandated count of every person living in the U.S. that happens every 10 years. We answer your questions and help you strategize for changes to come with an overview of who draws congressional districts (and when redistricting occurs), how the redistricting process works, and projections from the 2020 Census.

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Who draws congressional districts?

States have different processes for drawing congressional districts – and different governing bodies in charge, including Republican- or Democratic-controlled state legislatures. Some states have divided government, while in others the line will be drawn by independent or bipartisan commissions.

The party in charge can often redraw those lines to give itself an advantage. By dividing the opposition party’s likely voters among several districts, partisan mapmakers can craft strong and difficult-to-flip districts for their party, a process known as gerrymandering.

Six states adopted new systems for drawing lines, intended to force bipartisan consensus, sometimes by using commissions. Partisan power still carries considerable influence in 28 states.

The path to a commission

Though legislators still take charge of redistricting in most states, a growing number of states have been shifting power away from legislators in favor of commissions. In 2000, Arizona voters approved granting redistricting power to an independent commission – a ballot measure intended to end gerrymandering.

The Arizona commission comprises five members: two Democrats, two Republicans, and an independent chair. Lawmakers appoint the four partisan members from a pool of applicants, and the partisan members select the independent chair. Though lawmakers play a role in selecting the commissioners, they do not get to vote on the updated maps.

Watch: Who Draws the Lines – Monitoring Developments in Redistricting

This webinar, featuring analysis by Bloomberg Government and the National Conference of State Legislatures, provides an overview of who draws congressional districts, how the redistricting process works in various states, and early projections that can be made on the outcome.

When does redistricting occur?

The redistricting process starts with the release of data from the Census, a constitutionally mandated count of every person living in the U.S., which happens every 10 years. The count will determine which states gain seats in the U.S. House of Representatives, and which ones lose. (The Senate count remains the same, with two members from each state, elected statewide, regardless of population.)

State population numbers are due at the end of the year in which the Census was conducted. Results from the 2020 Census were due December 31, 2020, but were delayed until April 2021 because of the Covid-19 pandemic.

On August 12, 2021, the U.S. Census Bureau released another set of numbers with block-by-block population countsCensus blocks – laid out once every 10 years – are statistical areas defined by geographic features and nonvisible boundaries, like railroad tracks, roads, or property lines. These designations allow states to draw districts of equal size to account for population shifts over the past decade.

How often does redistricting occur?

States redraw legislative district boundaries every 10 years. Courts may invalidate maps mid-decade and either impose new lines or direct legislatures to do so, as was the case last decade in Florida, North Carolina, Virginia, and Pennsylvania.

How does the redistricting process work?

Following the completion of the Census, most states retain the same number of congressional seats – but some gain or lose seats in the House through reapportionment.

  1. U.S. Census Bureau delivers initial state population numbers to states.
  2. The bureau delivers a second set of detailed, block-by-block population counts to states.
  3. States can begin the redistricting process according to their respective systems.
  • However, law requires that the districts be about equal in population.

How congressional districts are determined and drawn

States can begin redrawing congressional district maps when they get the detailed figures from the Census Bureau – which count the number of people down to the block level. This data is important to ensure that every district within the same state is of about equal population.

Mapmakers have latitude in how they redraw district lines, though the Constitution requires that districts be about equal in population, and the Voting Rights Act holds that maps can’t harm voters based on their race or ethnicity.

State constitutions and statutes may have additional rules or criteria.

How the 2020 Census will shape the 2022 political landscape

Redistricting will have a major impact on the political landscape in 2022 and beyond – but it’s also not the sole determinant in future election outcomes:

  • Redistricting, performed by state legislatures or independent commissions, will set up the fight for the House of Representatives for the next decade, starting with the first midterm election under President Biden.

Democrats control the House by less than half a dozen seats – one of the smallest margins for either party in decades – and a shift of a few seats could tip power back to the GOP as soon as the 2022 elections.

  • Redistricting doesn’t guarantee results. Incumbent retirements, candidate recruitment, campaign quality, and Biden’s approval rating will affect the outcome of the 2022 elections.

Gainers & Losers from the 2020 Census

Texas gained the most seats in Congress, with states in the industrial North losing the most. California lost a seat for the first time ever.

Congressional seats
  • Texas is the only state that gained two districts while Colorado, Florida, Montana, North Carolina, and Oregon each won one additional seat.
  • 7 states lost one seat: California, Illinois, Michigan, New York, Ohio, Pennsylvania, and West Virginia. California lost a seat for the first time ever.
  • New York lost a seat after falling short by just 89 residents, though it was in danger of losing two districts.
    • Sun Belt states benefited from booming Latino populations and from people moving from more liberal states – like New York.

Congressional Reapportionment and the 2020 Census

Reapportionment is a zero-sum game. For more than a century, House membership has remained at 435 – for one state to gain representation, another must lose.

  • The total U.S. population for apportionment was 331,108,434 as of April 1, 2020.
  • The average House district will have 761,169 people, up from 710,767 in 2010, though numbers vary widely by state.