Momentum and Social Learning in Presidential Primaries

This paper investigates social learning in sequential voting systems. In the econometric model, candidates experience momentum effects when their performance in early states exceeds expectations. The empirical application uses daily polling data from the 2004 presidential primary. We find that Kerry benefited from surprising wins in early states and took votes away from Dean. Owing to these momentum effects, early voters had up to five times the influence of late voters in the selection of candidates, and this helps to explain the distribution of advertising expenditures. Finally, we use the estimated model to conduct two counterfactual experiments.