The Cook Partisan Voting Index, abbreviated PVI or CPVI, is a measurement of the partisanship of a U.S. congressional district or U.S. state.[1] This partisanship is indicated as lean towards either the Republican Party or the Democratic Party,[2] compared to the nation as a whole, based on how that district or state voted in the previous two presidential elections.[3][4]
History
The Partisan Voting Index was developed in 1997 by Charlie Cook of The Cook Political Report, in conjunction with Clark Bensen and his political statistical analysis firm, Polidata, "as a means of providing a more accurate picture of the competitiveness".[5][6][7] It is based on the methodology introduced by Rob Richie of the Center for Voting and Democracy for the Center's July 1997 Monopoly Politics report.[8][9]
The Cook Political Report has since released new PVI scores every two years.[10] In 2021, the newsletter ended its relationship with Polidata and instead used Dave Leip's Atlas of U.S. Presidential Elections to calculate 2020's results.[7] The most recent iteration is the 2025 Cook Partisan Voting Index.[11]
Calculation and format
The index looks at how every congressional district voted in the past two presidential elections combined and compares it to the national average.[12] The Cook PVI is displayed as a letter, a plus sign, and a number, with the letter (either a D for Democratic or an R for Republican) indicating the party that outperformed in the district and the number showing how many percentage points above the national average it received.[10] In 2022, the formula was updated to weigh the most recent presidential election more heavily than the prior election.[13]
By congressional district
The PVIs for congressional districts are calculated based on the 2020 and 2024 presidential elections.[11] With a PVI of R+1, was determined to be the median congressional district, meaning that exactly 217 districts are more Democratic and exactly 217 are more Republican than this district.[11] As of 2025, 219 districts are more Republican than the national average, 207 districts are more Democratic than the national average, and nine districts match the national average. The number of swing seats, defined as those between D+5 and R+5,[citation needed] is 97.[11]
| District | PVI | Party of representative |
|---|---|---|
By state
The PVIs for states are calculated based on the results of the U.S. presidential elections in 2020 and 2024.[14] The table below reflects the state of Congress and governors, based on the 2024 election results.
Using the United States Census Bureau's official 2024 population estimates, a combined 182,737,780 residents live in the 29 states that lean Republican; 141,264,067 residents live in the 20 voting blocs (19 states plus Washington, D.C.) that lean Democratic; and 16,101,434 residents live in the two states (Michigan and Wisconsin) that lean neither Republican nor Democratic (PVI of EVEN).
See also
- Political party strength in U.S. states
- Psephology, the statistical analysis of elections
- Two-party-preferred vote
Notes
- ^ Includes an independent senator who caucuses with the Democrats
- ^ Includes an independent senator who caucuses with the Democrats
- ^ Mayor of the District of Columbia
- ^ Non-voting delegate
References
- ^ Paul, Megan; Zhang, Ruya; Liu, Bian; Saadai, Payam; Coakley, Brian A. (2022). "State-level political partisanship strongly correlates with health outcomes for US children". European Journal of Pediatrics. 181 (1): 273–280. doi:10.1007/s00431-021-04203-y. PMID 34272984
- ^ Cillizza, Chris (2017-04-10). "A map that shows we really do live in two different Americas". CNN. Retrieved 2023-12-15.
- ^ Cillizza, Chris (2018-03-14). "The differences between real grassroots and "Astroturf" matter". CNN. Retrieved 2020-11-29.
Which brings me to the Cook Political Report's Partisan Voting Index or PVI. The goal of the PVI is to compare every congressional district to every other congressional district based on how it has performed in each of the last two presidential elections.
- ^ Benen, Steve (2017-02-07). "There are 119 Republican House members who should be VERY nervous today". MSNBC. Retrieved 2020-11-29.
To get a sense of a congressional district's political leanings, there's a helpful metric called the Partisan Voter Index, or PVI, created 20 years ago by the Cook Political Report.
- ^ Kurtz, Josh (June 8, 2005). "Future House Opportunities Abound (Maybe)". Roll Call. Retrieved 22 December 2023.
- ^ State of Change. Boulder: University of Colorado Press. 2011. ISBN 978-1-4571-1154-9. Retrieved 22 December 2023.
- ^ "The Cook Partisan Voting Index (Cook PVI)". The Cook Political Report with Amy Walter. Cook Political Report. Retrieved 22 December 2023.
- ^ Cook, Charlie (August 11, 1997). "New Study Identifies 75 Seats That Should Be In Play for '98 Election". Roll Call. Retrieved 18 January 2024.
- ^ "Monopoly Politics". Center for Voting and Democracy. July 1997. Retrieved 18 January 2024.
- ^ Kane, Paul (April 8, 2023). "New report outlines the deep political polarization's slow and steady march". The Washington Post. Retrieved 22 December 2023.
- ^ Wasserman, David (April 3, 2025). "2025 Cook PVI℠: District Map and List (119th Congress)". Retrieved April 12, 2025.
- ^ Seib, Gerald (December 9, 1998). "GOP Moderates and the Agony Of Their Impeachment Choice". The Wall Street Journal. Retrieved 22 December 2023.
- ^ Wasserman, David (July 13, 2022). "Introducing the 2022 Cook Partisan Voting Index (Cook PVI)". The Cook Political Report with Amy Walter. Retrieved 2022-07-13.
- ^ "2025 Cook PVI℠: State Map and List". Cook Political Report. 2025-03-06. Retrieved 2025-05-10.