Voting games with endogenously infeasible coalitions

While they use the language of game theory the known measures of a priory voting power are hardly more than statistical expectations assuming the random behaviour of the players. Focusing on normalised indices we show that rational players would behave di erently from the indices' predictions and propose a model that captures such strategic behaviour. In our model players do not automatically participate in every winning coalition they are members of, but have the possibility to block the formation of such a coalition. The strategic use of such blocks can increase voting power, when the latter is de ned over the game with the remaining winning coalitions. In our model players do not automatically participate in every winning coalition they are members of, but have the possibility to block the formation of such a coalition. The strategic use of such blocks can increase voting power, when the latter is defined over the game with the remaining winning coalitions.