Our current model based forecast for the Republican two-party vote is 47.0% (02 November 2008).

This forecast is calculated by combining the predictions of all available quantitative models. It is incorporated in the Pollyvote with a weighting of 25%.

Over the last several election cycles, political scientists and economists have employed regression models of past elections to forecast the percent of the two-party vote going to the incumbent party candidate in the next election.

Most models consist of between two and seven variables and are estimated over anywhere between scarcely over a dozen elections to close to twice as many. (By contrast, historian Alan Lichtman uses 13 “Keys” to predict whether the incumbents will be reelected.)

A common denominator across most quantitative models is at least one measure of economic conditions, although no two employ the same metrics. Also, most models include at least one public opinion variable, a trial heat poll or a presidential approval rating, although here again there is no unanimity on indicators.

Additional information

Jim Campbell as well as Michael Lews-Beck & Charles Tien generated two forecasts. In this case, Polly incorporated the preferred forecast of the forecaster. The alternative forecasts were

• Jim Campbell: McCain 52.2%
• Michael Lewis-Beck & Charles Tien: McCain 43.43%