In a federal union, a referendum paradox occurs each time a decision taken by representatives elected in separate jurisdictions (districts, states, regions) conflicts with the decision that would have been adopted if the voters had directly given their opinion via a referendum (Nurmi 1999)....

Even, and in fact chiefly, if two or more players in a voting game have on a binary issue independent opinions, they may have interest to form a single voting alliance giving an average gain of influence for all of them. Here, assuming the usual independence of votes, we first study the alliance...