The Cook Partisan Voting Index, abbreviated PVI or CPVI, is a measurement of how partisan[1] a United States congressional district or state is. This partisanship[2] 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.[3][4]
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 (FairVote 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 2022 Cook Partisan Voting Index, which was released with an updated formula for calculating PVI values.[11]
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.[11]
The PVIs for congressional districts are calculated based on the 2016 and 2020 presidential elections.[11] With a PVI of R+1, Michigan's 8th congressional district was determined to be the median congressional district, meaning that exactly 217 districts are more Democratic and 217 are more Republican than this district.[11] As of 2022[update], in the House, there are 222 districts more Republican than the national average, and 206 districts more Democratic than the national average. The number of swing seats, defined as those between D+5 and R+5, is 87.[11]
The PVIs for states are calculated based on the results of the U.S. presidential elections in 2016 and 2020.[13] The table below reflects the current state of Congress and governors, based on the most recent election results.
State | PVI | Party of governor |
Party in Senate |
House balance |
---|---|---|---|---|
Alabama | R+15 | Republican | Republican | 6R, 1D |
Alaska | R+8 | Republican | Republican | 1D |
Arizona | R+2 | Democratic | Democratic* | 6R, 3D |
Arkansas | R+16 | Republican | Republican | 4R |
California | D+13 | Democratic | Democratic | 40D, 12R |
Colorado | D+4 | Democratic | Democratic | 5D, 3R |
Connecticut | D+7 | Democratic | Democratic | 5D |
Delaware | D+7 | Democratic | Democratic | 1D |
Florida | R+3 | Republican | Republican | 20R, 8D |
Georgia | R+3 | Republican | Democratic | 9R, 5D |
Hawaii | D+14 | Democratic | Democratic | 2D |
Idaho | R+18 | Republican | Republican | 2R |
Illinois | D+7 | Democratic | Democratic | 14D, 3R |
Indiana | R+11 | Republican | Republican | 7R, 2D |
Iowa | R+6 | Republican | Republican | 4R |
Kansas | R+10 | Democratic | Republican | 3R, 1D |
Kentucky | R+16 | Democratic | Republican | 5R, 1D |
Louisiana | R+12 | Republican | Republican | 5R, 1D |
Maine | D+2 | Democratic | Both* | 2D |
Maryland | D+14 | Democratic | Democratic | 7D, 1R |
Massachusetts | D+15 | Democratic | Democratic | 9D |
Michigan | R+1 | Democratic | Democratic | 7D, 6R |
Minnesota | D+1 | Democratic | Democratic | 4D, 4R |
Mississippi | R+11 | Republican | Republican | 3R, 1D |
Missouri | R+10 | Republican | Republican | 6R, 2D |
Montana | R+11 | Republican | Both | 2R |
Nebraska | R+13 | Republican | Republican | 3R |
Nevada | R+1 | Republican | Democratic | 3D, 1R |
New Hampshire | D+1 | Republican | Democratic | 2D |
New Jersey | D+6 | Democratic | Democratic | 9D, 3R |
New Mexico | D+3 | Democratic | Democratic | 3D |
New York | D+10 | Democratic | Democratic | 16D, 10R |
North Carolina | R+3 | Democratic | Republican | 7D, 7R |
North Dakota | R+20 | Republican | Republican | 1R |
Ohio | R+6 | Republican | Both | 10R, 5D |
Oklahoma | R+20 | Republican | Republican | 5R |
Oregon | D+6 | Democratic | Democratic | 4D, 2R |
Pennsylvania | R+2 | Democratic | Democratic | 9D, 8R |
Rhode Island | D+8 | Democratic | Democratic | 2D |
South Carolina | R+8 | Republican | Republican | 6R, 1D |
South Dakota | R+16 | Republican | Republican | 1R |
Tennessee | R+14 | Republican | Republican | 8R, 1D |
Texas | R+5 | Republican | Republican | 25R, 13D |
Utah | R+13 | Republican | Republican | 4R |
Vermont | D+16 | Republican | Democratic* | 1D |
Virginia | D+3 | Republican | Democratic | 6D, 5R |
Washington | D+8 | Democratic | Democratic | 8D, 2R |
West Virginia | R+22 | Republican | Both | 2R |
Wisconsin | R+2 | Democratic | Both | 6R, 2D |
Wyoming | R+25 | Republican | Republican | 1R |
* Includes an independent senator who caucuses with the Democrats. |