Alberto Alesina and Howard Rosenthal argue that surprise about the outcomes of US presidential elections accounts for two important features of the American political economy: the regular loss of votes experienced by the president's party in midterm congressional elections, and the systematic relationship between the party of the incoming president and macroeconomic performance. Scholars recently have begun conducting rigorous tests of the relationship between surprise and economic performance, but no similar empirical work exists on how surprise affects midterm elections. In this article, we offer the first direct test of the proposition that electoral surprise drives the midterm loss. Our analysis shows that the more surprised moderate voters are about the outcome of a presidential election, the lower the probability that they will support the president's party in the following midterm contest.