Forecasting the presidential vote in the states, 1948-2004: An update, revision, and extension of a state-level presidential forecasting model

This research updates, revises, and extends a forecasting equation of the presidential vote in the states. The original equation was composed of sixteen predictors available well before the election and estimated with data from 531 state elections from 1948 to 1988. The equation was empirically strong, based on objective predictors, and more parsimonious than previous equations. Reexamining the equation with 200 additional state elections from 1992, 1996, 2000, and 2004 indicates that the equation remains well supported, but suggests several opportunities for improvement. A revised equation has a mean absolute error of 3.2 percentage points and correctly predicts 87 percent of all electoral votes. The extension of the analysis adapts the forecast equation to predict electoral vote winners, conducting a logit analysis that takes into account both the size of the state and the closeness of its previous election. This produces more accurate forecasts of both electoral vote winners in the states and the division of the aggregate national electoral vote.