Indecision Theory: Weight of Evidence and Voting Behavior

In this paper, we show how to incorporate weight of evidence, or ambiguity, into a model of voting behavior. We do so in the context of the turnout decision of instrumentally rational voters who differ in their perception of the ambiguity of the candidates' policy positions. Ambiguity is reflected by the fact that the voter's beliefs are given by a set of probabilities, each of which represents in the voter's mind a different possible scenario. We show that a voter who is averse to ambiguity considers abstention strictly optimal when the candidates' policy positions are both ambiguous and they are "ambiguity complements." Abstaining is preferred since it is tantamount to mixing the prospects embodied by the two candidates, thus enabling the voter to "hedge" the candidates' ambiguity.