Johnston (1978), Deegan andPackel (1979), andHoller (1982) proposed three power indices for simple games: Johnston index, Deegan-Packel index, and the Public Good Index. In this paper, methods to compute these indices by means of the multilinear extension of the game are presented. Furthermore, a new characterization of the Public Good Index is given. Our methods are applied to two real-world examples taken from the political field.