Do voters vote ideologically?

In this paper we address the following question: To what extent is the hypothesis that voters vote "ideologically" (i.e., they always vote for the candidate who is ideologically "closest" to them) testable or falsifiable? We show that using data only on how individuals vote in a single election, the hypothesis that voters vote ideologically is irrefutable, regardless of the number of candidates competing in the election. On the other hand, using data on how the same individuals vote in multiple elections, the hypothesis that voters vote ideologically is potentially falsifiable, and we provide general conditions under which the hypothesis can be tested.