Heuristics have rapidly become a core concept in the study of political behavior. The term heuristic stems from the ancient Greek heuriskein, which means “to discover.” In psychology and political science, the term is used to describe cognitive shortcuts in decision making under uncertainty. The key idea is that decision makers with limited time, information, or resources use such shortcuts, thereby bypassing a certain amount of information to reach appropriate decisions. In this sense, heuristics contrast with classical rational choice. Using heuristics allows efficient decision making but can lead to biases, errors, and suboptimal decisions. Heuristics allow decision makers to draw inferences, to fill in information gaps, and to form an impression of the decision at hand. Indeed, they may be the only way to come to grips with uncertainty, especially when a decision is urgent. In political science, the concept of heuristics, originating in mathematics, economics, and psychology, has long been hailed as a possible remedy to citizens’ lack of political knowledge. Citizens participate in democratic decisions, but these decisions often pose high cognitive and informational demands. Ideally, citizens with little information about a political issue or about a candidate could use heuristics in order to reach decisions resembling those of their more well-informed peers. More recently, however, the possible biases introduced by reliance on heuristics, in particular partisan bias and a lack of consideration of different alternatives, has received more attention. Moreover, some studies show that heuristics can be used most efficiently by voters who are relatively well informed and highly interested in politics. The question of whether, or under which circumstances, heuristics can be a useful tool for democratic decision making has not yet been answered conclusively.