NO. 1
COOK PARTISAN VOTING INDEX
Introduced in 1997, The Cook Partisan Voting Index (PVI) was developed for The Cook Political Report by Polidata Inc.
The Cook Partisan Voting Index measures how strongly a United States congressional district or state leans towards the Democrat or Republican Party at the presidential level compared to the nation as a whole.
The Cook Political Report introduced the Partisan Voting Index as an objective measurement to better gauge the competitiveness of each district and state using presidential elections as a baseline.
NO. 2
HYBRID PARTISAN VOTING INDEX
Modeled after the Cook Partisan Voting Index, the Hybrid Partisan Voting Index (hPVI) was developed for Wilkerson Public Affairs by Braedon Wilkerson in 2014.
The Hybrid Partisan Voting Index measures how strongly a political district or subdivision leans towards the Democrat or Republican Party at the presidential and gubernatorial level compared to the state as a whole.
The Hybrid Partisan Voting Index was introduced as an objective measurement to better gauge the competitiveness of political districts and subdivisions using presidential and gubernatorial elections as a baseline.
NO. 3
RACE RATINGS
This chart provides a spectrum that analyzes the competitiveness or vulnerability of partisan political districts and subdivisions each cycle.
Ratings are defined as follows:
Solid
These races are not considered competitive and are not likely to become closely contested.
R + D > 56%
Likely
These seats are not considered competitive at this point but have the potential to become competitive.
R + D = 55% - 54%
Lean
These are considered competitive races but one party has an advantage.
R + D = 53% - 52%
Swing
These are the most competitive races; either party has a good chance of winning.
R + D = 51% - 49%
NO. 4
CALCULATIONS
PVIs are calculated by comparing a district's average Democrat or Republican Party share of the two-party presidential and gubernatorial votes in the past presidential and gubernatorial elections as compared to the states average share of the same.
The statewide average in 2012 was approximately 54.57% Democrat to 45.43% Republican.
For example, in Washington’s 43rd Legislative District, Democrat candidates won an average 85.85% of the two-party share in the 2012 presidential and gubernatorial elections, respectively.
Comparing the average of those two results (85.85%) against the average statewide share of the same (54.57%), the district voted approximately 31 percentage points more Democrat, or D+31.
Additionally, in Washington’s 13th Legislative District, Republican candidates won an average 64.73% of the two-party share in the 2012 presidential and gubernatorial elections, respectively.
Comparing the average of those two results (64.73%) against the average statewide share of the same (45.43%), the district voted approximately 19 percentage points more Republican, or R+19.
Following the presidential and gubernatorial elections, presidential and gubernatorial results are compiled to generate Hybrid Partisan Voting Index scores for statewide offices, congressional districts, and political districts or subdivisions including state legislative districts, counties, cities, and precincts.
Calculations are rounded to the nearest whole percent within .5 a percentage point.