Forecasting the Presidential Vote in 2004: Placing Preference Polls in Context

Abstract

The trial-heat poll and economy forecasting model is a simple model based on a simple principle. The model uses just two predictor variables to forecast the in-party presidential candidate's share of the national two-party popular vote. The first is the in-party presidential candidate's share of support between the major party candidates in the Gallup Poll's trial-heat (or preference) poll question around Labor Day. The second predictor is the Bureau of Economic Analysis' (BEA) measure of real growth in the Gross Domestic Product (GDP) in the second quarter of the election year (April through June). The GDP measurement is the “preliminary” measure released by the BEA at the end of August, the latest available in time to be used in the forecast. An in-party presidential candidate who is the incumbent is accorded full responsibility for the economy in the equation and a successor or non-incumbent in-party candidate is accorded half the credit or blame for the growth or decline in the economy. This partial credit or blame for successor candidates refl ects both past experience in forecasting (Campbell 2000) and independent findings regarding the effects of retrospective evaluations of the economy on voting behavior (Nadeau and Lewis-Beck 2001). The regression estimated forecasts based on these two predictors, estimated over the 14 presidential elections from 1948 to 2000, is a mix of about two-thirds trial-heat poll and one-third economic growth. In essence, with the preference poll at the center of the prediction, the forecast may be interpreted as an adjusted preference poll.