This article develops a reputational theory of political falsehoods. Politicians are motivated by the desire to build a positive reputation, therefore, they will be more likely to deliver false statements (incurring the risk of being fact-checked) when the potential benefit outweighs the cost. This happens as new elections come closer, since the electoral benefit of falsehoods increases along with the probability of being checked too late (after the election day). Politicians are less likely to issue falsehoods in detailed statements and in scripted communication, since the reputational cost is higher because such falsehoods would be considered intentional. Conversely, the stronger trust that voters attribute to politicians on issues they own, allows politicians to lie on such topics. Statistical analysis of almost 8000 statements released by politicians and assessed by fact-checkers, in the United States and Italy (2007–2018), supports the hypotheses. The results hold irrespective of party affiliation.