The minimax regret model of decision making under uncertainty, which was proposed by Ferejohn and Fiorina (1974) as a model of the voting decision, is here generalized to encompass forms of political participation (such as contributing money or time to a campaign) in which the range of alternatives is continuous. A principal implication of the model is that aggregate campaign contributions may be substantially increased by limiting the amount that any one individual can contribute. The conditions under which the behavior of a minimax regret decision maker can be unambiguously distinguished from that of an expected utility maximizer are also specified.