AbstractThe retrospective voting theory suggests that citizens vote for governing parties in response to distributive benefits. Knowing this, governments may reward voters by providing particularistic benefits—i.e., pork—prior to elections. Previous studies, however, do not account for the endogeneity. We address this problem by focusing on disaster relief and exploiting exogeneity of disaster. In particular, by using maximum hourly rainfall as an instrumental variable for disaster relief, we analyze the causal effect of disaster relief on incumbent’s electoral outcomes. Our analyses of Japanese data in the past few decades indicate that disaster relief increased governing parties’ vote share. Specifically, when the disaster relief per capita increases from zero to its mean, the predicted value of the governing parties’ vote share increases by 2.8 and 5.4% points in the lower and upper chambers, respectively. The finding is consistent with retrospective voting behavior. Moreover, our results imply that the incumbent’s electoral gain is brought about by persuading voters from oppositions to governing parties rather than by mobilizing supporters of governing parties.