What is the Cook PVI℠?
What do the scores mean?
How is the Cook PVI different from race ratings?
2025 Cook PVI Report Now Available
One of the biggest takeaways of this years report is that district-level polarization has actually ticked down slightly even as America’s ideological divisions seem to deepen.

The Cook Partisan Voting Index (Cook PVI℠) Explained
In August of 1997, The Cook Political Report introduced the Cook Partisan Voting Index (Cook PVI) as a means of providing a more accurate picture of the competitiveness of each of the 435 congressional districts. Whereas our race ratings reflect our outlook for which party will win the next election in each state and district, the Cook PVI takes a longer view and seeks to measure the underlying partisanship of each district relative to the nation as a whole.
We have released new PVI scores following every election and instance of redistricting since 1996, each time taking into account the prior two presidential elections. Prior to 2020, the Cook Political Report contracted with Clark Bensen's firm Polidata to calculate presidential results by congressional districts and PVI scores. Starting in 2021, the Cook Political Report teamed up with Dave Leip's Atlas of U.S. Presidential Elections to calculate 2020 and 2024 results by congressional district.
Because redistricting took place after the 2020 election, we also needed to use updated 2020 election results for all 435 newly drawn districts in order to calculate 2025 PVI scores. To do that, we relied on data publicly available via Dave's Redistricting App, a free online mapping tool originally developed by Dave Bradlee that allows any user to draw and evaluate district boundaries. The app uses precinct-level election data largely compiled by the Voting Election & Science Team (VEST), a consortium of academic researchers.
The Cook Partisan Voting Index is an attempt to identify an objective measurement of each congressional district and state. While other data such as the results of senatorial, gubernatorial, congressional and other local races can help fine-tune the exact partisan tilt of a particular district, those kinds of results don’t allow a comparison of districts across state lines. Only presidential results allow for total comparability.
A Partisan Voting Index (PVI) score of D+2, for example, means that in the 2020 and 2024 presidential elections, the state or district performed about two points more Democratic in terms of two-party vote share than the nation did as a whole, while a score of R+4 means the state or district performed about four points more Republican. If a state or district performed within half a point of the nation in either direction, we assign it a score of EVEN.
To determine the "national value" for these latest Cook PVI scores, we've taken a weighted (75/25) average of the Democratic share of the two-party presidential vote in 2024 and 2020, which is roughly 50.005 percent. So, if Kamala Harris and Joe Biden both carried 57% of the vote in a given district in 2024 and 2020 respectively, the district would have a PVI score of roughly D+7. If they only carried 46%, the district would have a PVI score of R+4.
Notes about Cook PVI Data & Methodology
Following each election and round of redistricting, presidential results are compiled to generate PVI scores for each congressional district. In a few states, district-level presidential results are aggregated by state and/or local election authorities. However, in many they are not, and authorities report many absentee/early votes centrally rather than redirecting them back to the voter’s precinct. The record numbers of early and absentee ballots cast in 2020 and 2024 compounded the challenge of allocating presidential results to districts in some states.
For the 2025 PVI dataset, Dave Leip's Atlas of U.S. Presidential Elections used best estimates in the case of split precincts and counties, disaggregating 2024 results to the census block level and assigning unallocated presidential votes in proportion to vote totals for congressional candidates where applicable. For the 2020 results used to calculate the 2025 Cook PVI dataset, Dave's Redistricting App's approach to disaggregating results to the census block level can be found here. Per DRA, "disaggregation of 2016-2021 data uses VEST's method."
COOK PVI℠ is a service mark of Invincible Summer Media, Inc.
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