Social interactions in voting behavior: distinguishing between strategic voting and the bandwagon effect

Prior studies of strategic voting in multi-party elections potentially overestimate the extent of it by counting erroneously votes cast under different motivations as strategic votes. We propose a method that corrects some of this overestimation by distinguishing between strategic voting (voting for a candidate other than the most preferred one to reduce the likelihood of an election victory by a third candidate that is disliked even more) and the votes cast under the ‘bandwagon effect’ (voting for the expected winner instead of the most preferred party to conform to the majority or to be on the winning side). Our method follows from the observation that a vote cannot be strategic unless the voter believes that it will affect the outcome of the election with a non-zero probability, while a vote cast under the bandwagon effect requires no such belief. Employing survey data that include the respondent’s assessment of the importance of his vote, we illustrate this method by estimating the extent of strategic voting in the 2005 UK general election. The estimated extent of strategic voting (4.22%) is strictly less than self-reported strategic voting (6.94%), but the discrepancy cannot be attributed in a statistically significant way to the bandwagon effect, suggesting that motivations other than those identified in the literature may be at work.