Complete information pivotal-voter model with asymmetric group size and asymmetric benefits

We analyze a standard pivotal-voter model under majority rule, with two rival groups of players, each preferring one of two public policies and simultaneously deciding whether to cast a costly vote, as in Palfrey and Rosenthal (1983). We allow the benefit of the favorite public policy to differ across groups and impose an intuitive refinement, namely that voting probabilities are continuous in the cost of voting to pin down a unique equilibrium. The unique cost-continuous equilibrium depends on a key threshold that compares the sizes of the two groups.