Although most political party systems in Latin America have relatively few major parties, and in many case those parties fall relatively closely together ideologically, the countries of Latin America have consistently struggled with political instability. This article argues that an important factor contributing to the varying stability of political parry systems concerns how major parties compete. Party systems with a moderate level of competition, in which opposing parties have distinct positions, authentically attempt to defeat their opponents, but accept as legitimate an opposition win, tend to be the most stable. Party systems become relatively less stable with either more or less competition. Party systems with combative party relations, in which parties do not accept the right of the opposition to win, tend to be the most unstable, as the primary competitors may themselves be inclined to support the usurpation of democracy. However, party systems with collusive party relations, in which major parties cooperate closely through pacted or consociational arrangements, may also contribute to instability. These arrangements may initially facilitate democratization during transition periods, but over time the stagnating party system may fail to keep pace with a changing society. Limited opportunities for new political parties and a loss of representativeness by the older parties encourage the development of anti-system parties.
