Electoral competition among a high number of parties and the formation of multiparty coalition governments are typical features of most democratic regimes. In contrast, two-party systems producing single-party governments are characteristic of a few of the oldest, institutionally frozen democracies, including the United Kingdom of Britain and the United States of America. In the past, two-party systems were considered a sound formula for effective and stable government. But the expansion of suffrage rights and the diffusion of democratic regimes, not only in continental Europe but also across the rest of the world, has confirmed Robert Dahl’s early intuition: “It might be reasonable to consider multiparty systems as the natural way for government and opposition to manage their conflicts in democracies, while two-party systems, whether resembling the British pattern or the American, are the deviant cases” (1966, p. 334).
The degree of multipartyism can be measured not only by the absolute number of parties in the system, but also by their relative size. For this purpose, several indices of fractionalization, including the “effective number” of parties, have been proposed in which each party is weighed by its proportion of either votes or seats (depending on the electoral or legislative focus of the analysis). A conventional estimate is that multiparty systems exist when there are at least three effective parties. In other words, there is still a two-party system, even if there are more than two parties in the assembly, if two of the parties are sufficiently large (as happens, for instance, in the British House of Commons). About three-fourths of more than eighty democratic countries with more than one million inhabitants at the beginning of the twenty-first century have multiparty systems, that is, more than three effective electoral parties.
In any complex society, multiple parties can be formed on the basis of the politicization of new issues if political entrepreneurs take the initiative to introduce policy proposals alternative to the status quo. Potential issues to be politicized include defense, security, taxes, freedom, trade, school, property, family, welfare, the environment, race, and so on. The corresponding parties raising new policy alternatives have historically been called conservatives, liberals, radicals, socialists, Christians, agrarians, greens, ethnic, regionalists, and many other labels. In two-party systems, the agenda can be manipulated by shifting salience to only one or a few issues at a time, which usually produces high polarization between the two parties. In multiparty systems, by contrast, multiple policy issues can be given salience by different parties at the same time, thus broadening the public agenda and the opportunities for citizens’ choice.
There has been some discussion over the propensity of multiparty systems to promote either “moderate” or “polarized” electoral competition. Polarization indices capture the degree of party concentration of votes or seats and the relative distance between various parties’ policy positions. Obviously, polarization is minimal when there is only one, internally compact party—that is, when all voters prefer the same policy, which is indeed a rare occurrence in a democratic regime. But polarization is maximal when the number of parties is two, they have similar size, and are located at a great distance from each other. In countries with more than two parties, the higher the number of parties, the lower their relative distances (because intermediate, relatively close positions emerge), and the lower the degree of polarization in electoral competition among them.
A traditionally illustrative case is Switzerland, where there are a high number of parties and a high degree of policy consensus among them. Systematic analyses have shown that, in general, high fractionalization, that is, a high number of parties, is associated with low polarization.
In fact, most democratic party systems have moderate degrees of both party fractionalization and party polarization. At the beginning of the twenty-first century, multiparty systems exist in democratic countries such as Argentina, Belgium, Brazil, Costa Rica, the Czech Republic, Denmark, Finland, France, Germany, Indonesia, Israel, Japan, the Netherlands, New Zealand, Norway, Poland, Sweden, Switzerland, as well as in the European Parliament and many other institutions.
In multiparty assemblies, decision-making usually requires the formation of majority multiparty coalitions. In most parliamentary regimes, cabinets are formed with more than one party. In regimes with separate powers, multiparty coalitions are also frequently formed both for legislative decisions and in support of presidential cabinets.
When parties form coalitions, they usually prefer partners with relatively close policy and ideology positions in order to maintain consistency with their own positions and win voters’ credibility. As a consequence, majority coalitions typically include the median legislator’s party, which can be located around a centrist, moderate position. If there is proportional representation, the median party corresponds to the median voter’s choice. As the median voter’s position minimizes the sum of distances from all the voters, this outcome can be considered relatively socially efficient. In contrast, in a two-party system with a majoritarian electoral rule, a single party may receive a majority of seats in the parliament on the basis of a minority of popular votes, which does not necessarily include the median voter. On average, multiparty coalition cabinets based on proportional representation are substantially closer to the median voter’s position than are single-party cabinets based on plurality or majority rules.
In multiparty cabinets, the distribution of offices among parties may follow two criteria. On some issues of general interest, such as economic policy and interior and foreign affairs, the parties in the coalition tend to compromise on intermediate and moderate policies. Over time, even if some partners of the successive governmental coalitions change, there is a significant degree of consensus and continuity on major policies, in contrast to frequent policy reversals when single-party governments alternate. On other issues, separate portfolios are allocated to different parties according to the issue on which they are most prominently defined—such as finance for liberals, education for Christians, labor for socialists, agriculture for agrarians, environment for greens, culture for regionalists, etc.—which may satisfy people with intense issue preferences.
The formation of multiple parties promotes the choice of inclusive political and electoral institutions. In general, if there are only one or two large parties they prefer small assemblies and single-member electoral districts with plurality rule, that is, institutions able to exclude others from competition. In contrast, multiple small parties prefer large assemblies and large electoral district magnitudes (that is, high numbers of seats per district), the latter using proportional representation rules, able to include them in the system.
But the pressures from multiparty systems to adopt inclusive electoral rules work differently in countries of different size. In large countries, a large assembly with the number of seats positively correlated to the country’s population can be sufficiently inclusive. In the United States, for instance, the ideological range of Congress members, in spite of belonging formally to only two parties, is similar to that of typical multiparty systems in Europe, including conservative, Christian-democratic, liberal, and social-democratic positions. This derives from the fact that each representative is elected by the rather homogeneous population of a small territory in a very large and heterogeneous country. The two parties are large umbrellas for varied representation.
By contrast, in small countries in which small assemblies do not create large room for political variety, the development of multiple parties favors more strongly the adoption of inclusive, large multimember districts with proportional representation rules. A relevant development is that the average size of democratic countries decreases as a consequence of the fact that the number of countries and the number of democracies in the world increase. As the number of parties also increases within each democratic country, more and more countries tend, thus, to adopt electoral systems with rules of proportional representation.
All in all, traditional two-party systems, which reflected early political developments in relatively simple societies with limited suffrage rights, have been associated in recent times with high electoral polarization, adversarial politics, socially biased, minority governments, and policy instability. In contrast, multiparty systems, which result from widespread and continuing initiatives for policy and ideology innovation in democratic countries, are associated with inter-party competition and cooperation, broad public agendas, coalition governments with majority social support, consensual and relatively stable policy-making, and inclusive political institutions.
SEE ALSO Democracy; First-past-the-post; Party Systems, Competitive; Plurality
Powell, G. Bingham. 2000. Elections as Instruments of Democracy. New Haven, C T, and London: Yale University Press.
Sartori, Giovanni. 1976. Parties and Party Systems. Cambridge, U.K., and New York: Cambridge University Press.
Shepsle, Kenneth. 1991. Models of Multiparty Electoral Competition. London: Harwood.
Josep M. Colomer