The Cook Partisan Voting Index, abbreviated PVI or CPVI, is a measurement of how partisan a U.S. congressional district or U.S. state is. This partisanship is indicated as lean towards either the Republican Party or the Democratic Party, compared to the nation as a whole, based on how that district or state voted in the previous two presidential elections.

History

The Partisan Voting Index was developed in 1997 by Charlie Cook of ''

The Cook Political Report Amy Elizabeth Walter (born October 19, 1969)"Profile: Amy Walter"
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. The Cook Political Report has since released new PVI scores every two years. 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. The most recent iteration is the 2025 Cook Partisan Voting Index.

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. 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. In 2022, the formula was updated to weigh the most recent presidential election more heavily than the prior election.

By congressional district

The PVIs for congressional districts are calculated based on the

2020 The year 2020 was heavily defined by the COVID-19 pandemic, which led to global Social impact of the COVID-19 pandemic, social and Economic impact of the COVID-19 pandemic, economic disruption, mass cancellations and postponements of even ...

and

2024 The year saw the list of ongoing armed conflicts, continuation of major armed conflicts, including the Russian invasion of Ukraine, the Myanmar civil war (2021–present), Myanmar civil war, the Sudanese civil war (2023–present), Sudane ...

presidential elections. With a PVI of R+1, was determined to be the median congressional district, meaning that exactly 217 districts are more Democratic and 217 are more Republican than this district. , there are 218 districts in the House that are more Republican than the national average and 207 districts more Democratic than the national average. The number of swing seats, defined as those between D+5 and R+5, is 97.

By state

The PVIs for states are calculated based on the results of the U.S. presidential elections in

and

. The table below reflects the state of Congress and governors, based on the 2024 election results.

Notes

References

External links

The Cook Political Report
{{United States Congress Psephology United States congressional districts The Cook Political Report with Amy Walter