Omnibus or not: package bills and single-issue bills in a legislative bargaining game

Legislators sometimes pass unrelated issues in one bill with one vote (omnibus bills), but they often vote separately on different issues as well. In this article, a model is considered in which the first mover chooses whether to bargain over an omnibus bill or several separate bills. The main difference between the two types of bills is that trade-offs between issues are possible with omnibus bills, but not with separate bills. The underlying bargaining game is demand-bargaining (Morelli 1999). In this game, moderate legislators prefer to propose single-issue bills; extreme legislators prefer omnibus bills, if the asymmetry in policy ideal points in the legislature is large enough.