The Cook Political Report
The Cook Political Report, or the Cook Report for short, is the leading nonpartisan resource on likely election outcomes, redistricting, control of the House or U.S. Senate, and other future-looking political developments.
Charlie Cook founded it in 1984 after working as a staffer on Capitol Hill.
Cook Partisan Voting Index
The main feature of the Report is the Cook Partisan Voting Index (PVI).
There are actually two PVI's calculated: one for each state, and a separate for each Congressional district. The index is expressed as a letter (R for Republican, D for Democrat) followed by a plus sign and a number. The larger the number, the more likely that a state (or district) tends to vote for a particular political party.
Any state or district which voted within 0.5 percent of the national average is considered "Even".
The state calculation is based on the average of a state's voting in the two most recent Presidential elections, then compared to the national popular vote percentages. Similarly, the district calculation is based on the average of a district's voting in the same Presidential elections used for the state calculations, again compared to national percentages.
A detailed analysis of the ratings given by the Cook Report on election outcomes found that nearly 100% of the "Solid" category was correct, 95% of the "Likely" category proved right, and 85.7% of the "Lean" category became true. As to the "Toss Up" category, indeed about 49%-55% of of them were retained by the incumbent party.
- Although the District of Columbia is not a state nor does it have a Member of Congress, since it participates in Presidential elections due to the 23rd Amendment, a PVI is calculated for it as well.