Do not include Strategic Vision polls, as it is starting to seem likely those are not real polls. Same goes for Research 2000.
Include partisan and campaign-funded polls, as long as the full results are released to the public. (The more polls, the better).
Further, if there is more than one poll from a single organization, include all of them. (The more polls, the better).
The win % represents the chance for a Democratic victory given the current polling averages. It is based on my research into the 144 closest statewide campaigns from 2004-2010. For example, across those 144 campaigns, there is a 50% chance for the final polling average to differ from the final result by more than 1.76%. Thus, a candidate ahead by 1.76% is given a 75% chance of winning, since the polling average has an equal chance of being skewed in favor of either major-party candidate.
In campaigns where the general election matchup has not been decided, the win percentage used in the overall forecast features the two candidates who currently lead their respective primaries.
Campaigns where one party is ahead by 6.0 or more are considered "solid" (95% chance for leading party to win). Campaigns between 1.8 and 5.9 are considered "leans" (75-95% chance for leading party to win). Campaigns within 1.7 or less are considered "toss-ups." These categories are represented by the colors in the charts, and are included to make the chart more readable.
Candidates that have not officially entered the campaign are not included in the forecast.
Across the 52 closest general elections for Senate, Governor, and President (both swing state and national) from 2008-2010, here is how this methodology compares to fivethirtyeight.com and Pollster.com's:
Error rates, final predicted margin to final vote margin, 52 campaigns, 2008-2010