The Cook Partisan Voting Index (Cook PVI℠)

First introduced in 1997, the Cook Partisan Voting Index (Cook PVI℠) measures how each state and district performs at the presidential level compared to the nation as a whole.

What is the Cook PVI℠?

The Cook PVI measures how partisan a district or a state is compared to the nation as a whole.

What do the scores mean?

A Cook 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

How is the Cook PVI different from race ratings?

Whereas race ratings reflect our outlook for which party will win the next election in each state and district, PVI values take a longer view and seek to measure the underlying partisanship of each district relative to the nation as a whole.

2025 Cook PVI Report Now Available

The Cook Political Report is pleased to introduce the 2025 Cook Partisan Voting Index (Cook PVI℠) for all 435 congressional districts. For the last 28 years, the Cook PVI has been the gold-standard measurement of a congressional district’s partisan lean and provides key data points to help political professionals have access to the right analysis for getting it right.

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.

Read our full report

2025 Cook PVI

The 2025 Cook PVI scores were calculated using 2020 and 2024 presidential election results.

2023 Cook PVI

The 2023 Cook PVI scores were calculated following the 2021 round of redistricting, using 2016 and 2020 presidential election results. They are identical to the PVI scores released in 2022.

2021 Cook PVI

The 2021 Cook PVI scores were calculated using 2016 and 2020 presidential election results. They also reflect court-ordered changes to district boundaries in North Carolina prior to the 2020 election.

2019 Cook PVI

The 2019 Cook PVI scores were calculated using 2012 and 2016 presidential election results, updated to reflect court-ordered changes to district boundaries in Pennsylvania prior to the 2018 election.

2017 Cook PVI

The 2017 Cook PVI scores were calculated using 2012 and 2016 presidential election results. They also reflect court-ordered changes to district boundaries in Florida, North Carolina and Virginia prior to the 2016 election.

2015 Cook PVI

The 2015 Cook PVI scores were calculated using 2008 and 2012 presidential election results. They are identical to the PVI scores from the previous Congress.

2013 Cook PVI

The 2013 Cook PVI scores were calculated using 2008 and 2012 presidential election results.

2012 Cook PVI (Post-Redistricting)

The 2012 Cook PVI scores were calculated following the 2011 round of redistricting, using 2004 and 2008 presidential election results. They reflect the new district lines then set to take effect for the 113th Congress, but do not reflect the 2012 presiden

2011 Cook PVI

The 2011 Cook PVI scores were calculated using 2004 and 2008 presidential election results. They are identical to the PVI scores from the previous Congress.

2009 Cook PVI

The 2009 Cook PVI scores were calculated using 2004 and 2008 presidential election results.

2007 Cook PVI

The Cook 2007 PVI scores were calculated using 2000 and 2004 presidential election results, updated to reflect Republican-passed changes to district boundaries in Georgia and court-ordered changes to district boundaries in Texas prior to the 2006 election

2005 Cook PVI

The 2005 Cook PVI scores were calculated using 2000 and 2004 presidential election results.

2003 Cook PVI

The 2003 Cook PVI scores were calculated following the 2001 round of redistricting, using only 2000 presidential election results as 1996 results were not available for the newly redrawn congressional districts.

2001 Cook PVI

The 2001 Cook PVI scores were calculated using 1996 and 2000 presidential election results. They also reflect court-ordered changes to district boundaries in North Carolina prior to the 2020 election.

1999 Cook PVI

The 1999 Cook PVI scores were calculated using 1992 and 1996 presidential election results, updated to reflect court-ordered changes to district boundaries in North Carolina and Virginia prior to the 1998 election.

1997 Cook PVI

The 1997 Cook PVI scores were calculated following the 1996 elections, using the 1992 and 1996 presidential election results.

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.