ABSTRACT The attitudinal effects of mass shootings and terrorist attacks are well documented, but their electoral consequences have not been studied systematically in the American context. We derive a set of expectations about mass violence and electoral behavior from terror management theory and issue ownership theory. We then examine the effects of mass shootings and terrorist attacks on United States presidential elections from 1976 through 2016. We find mass shootings increase turnout in the counties where they occur. Furthermore, terrorist attacks reduce the Democratic presidential candidate's shares of the two-party vote at the county level. Both of these effects decay sharply as the time between the event and Election Day increases. These findings illustrate the power of mass violence to influence American electoral behavior, conditional on the type of violent event and its proximity to Election Day.