ABSTRACT
Political parties have long been recognized as key institutions in representative democracy. This chapter focuses on three specific purposes political parties serve which provide alternative rationales for their existence: mobilization of voters, choice of policy platforms and selection of politicians and the choice of electoral candidates. Voters have to decide whether to vote or abstain. Parties choose whether or not to compete in the election and, if so, which policy platform to propose. Decisions within each party are made by unanimity rule. The set of policy platforms a party can propose is represented by its Pareto set: the set of feasible policies that are efficient from the point of view of the party. The platform that receives the largest number of votes is then implemented by the elected representative of the party proposing the platform. By imposing discipline on the policy platforms that are offered by their politicians in an election, parties may affect equilibrium policy outcomes.
