Who Draws the Lines – Congressional Redistricting

Last Updated August 9, 2022

The once-a-decade battle to redraw the U.S. political map based on findings from the 2020 Census – a constitutionally mandated count of every person living in the U.S. – is complete, and in many states has spurred partisan clashes and ongoing litigation. We answer your questions and help you strategize for the complications created by shifting congressional districts with an overview of who draws the districts (and when redistricting occurs), how the redistricting process works, and how it’s likely to impact the 2022 midterm elections.

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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.

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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 Dec. 31, 2020, but were delayed until April 2021 because of the Covid-19 pandemic.

On Aug. 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 is shaping the 2022 political landscape

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 2022 midterm elections.

  • 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 in the 118th Congress.
  • Redistricting doesn’t guarantee results. Incumbent retirements, candidate recruitment, campaign quality, and Biden’s approval rating will affect the outcome of the 2022 midterms.

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Gainers and 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.

Redistricting and the 2022 midterm elections

Republicans controlled redistricting line-drawing in far more districts than Democrats and, as a result, should net several seats in the 2022 midterm elections from redistricting alone.

Republicans had final authority to draw congressional districts in 20 states vs. Democrats’ eight states, and the GOP “focused on putting a lot of their vulnerable incumbents into politically safe zones,” said Greg Giroux, Bloomberg Government’s senior elections reporter, at an elections outlook and state policy event hosted by Bloomberg Government and the State Government Affairs Council.

GOP-drawn maps will provide likely gains in states such as Florida and Ohio, while Democratic maps were thrown out in Maryland and New York.

“When all is said and done, we have almost exactly the same number of districts as Biden and Trump carried after redistricting as before – it was 224 to 211 before for Biden, and it’s 226 to 209 for Biden over Trump now,” Giroux said. “But the number of districts that Biden won by between five and 10 points rose by about six, so those districts are going to be highly competitive.”

Because midterm elections tend to hurt the sitting president’s party, Giroux added that he will be watching those competitive Biden-led districts “a lot more closely than I am even districts that Trump won by fewer than five points.”

Both parties have filed lawsuits to challenge maps they weren’t in charge of creating, and outstanding litigation could still alter district lines and affect the exact extent of the GOP’s redistricting advantage in the 2022 midterms.