In this paper we address the following questions: (i) To what extent is the hypothesis that voters vote sincerely testable or falsifiable? And (ii) in environments where the hypothesis is falsifiable, to what extent is the observed behavior of voters consistent with sincere voting? We show that using data only on how individuals vote in a single election, the hypothesis that voters vote sincerely 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 sincerely is potentially falsifiable, and we provide general conditions under which the hypothesis can be tested. We then assess whether the behavior of voters is consistent with sincere voting in U.S. national elections in the post-war period. We find that by and large sincere voting can explain virtually all of the individual-level observations on voting behavior in presidential and congressional U.S. elections in the data.