Do negative campaign advertisements affect voter turnout? Existing literature on this topic has produced conflicting empirical results. Some scholars show that negativity is demobilizing. Others show that negativity is mobilizing. Still others show that negativity has no effect on turnout. Relying on the psychology of decision making, this research argues and shows that this empirical stalemate is due to the fact that existing work ignores a crucial factor: the timing of exposure to negativity. Two independent empirical tests trace the conditional effect of negativity. The first test relies on data from the 2004 presidential campaign. The second test considers the effect of negativity over a broader period of time by considering elections 1976 to 2000. Taken together, both tests reinforce that negativity can only demobilize when two conditions are met: (1) a person is exposed to negativity after selecting a preferred candidate and (2) the negativity is about this selected candidate.