Parties and Party Systems: A Framework for Analysis

Sartori argues that a party counts only if it has coalition potential or blackmail potential. Coalition potential means it has been or could be a partner in governing coalitions; blackmail potential means its existence alters the direction of competition, even if it never governs [citation:3][citation:7]. This qualitative criterion replaces simple numerical counting, which Sartori considers inadequate because it cannot distinguish a fragmented system from a consolidated one [citation:19]. The rules are most fully applicable to parliamentary systems; in presidential systems, relevance is redefined as the ability to help or obstruct the election of the president and to secure congressional support [citation:11].

Sartori's typology classifies party systems by two criteria: format (number of relevant parties) and mechanics (ideological distance between the relevant extremes) [citation:20]. The main categories are: two-party systems (limited format, small distance); moderate pluralism (limited pluralism, small distance); polarized pluralism (extreme pluralism, large distance); and predominant party systems (one party regularly wins a qualified majority) [citation:20]. Sartori also identifies one-party systems and hegemonic party systems for non-competitive contexts [citation:16]. The distinction between moderate and polarized pluralism turns on whether competition is centripetal or centrifugal.

Sartori criticizes Duverger's laws for treating electoral systems as mechanical causes of party systems without accounting for the prior structuring of the party system [citation:14][citation:18]. His four statements replace Duverger's laws: a plurality system causes two-partyism only if the party system is structured and votes are evenly dispersed across districts; where dispersion is uneven, small parties are eliminated but more than two can survive [citation:18]. For proportional representation, Sartori argues that pure PR has no effect on the number of parties; the reductive effect comes from practical non-proportionality [citation:6][citation:18].

The most persistent criticism is that the typology has lost relevance, particularly for distinguishing two-party systems from moderate pluralism. One assessment argues that Sartori's framework cannot defend either the two-party/plurality argument or the moderate pluralism/PR argument because it underestimates the difference between the two types [citation:4]. The category of moderate pluralism has also become overcrowded, making it difficult to find unambiguous examples of genuine two-party systems [citation:20]. Critics also note that the counting rules are difficult to apply consistently across different institutional contexts.

Published by Cambridge University Press in 1976, the book was the first major attempt since Duverger's Political Parties (1951) to provide a general theory of party-based politics across democratic, authoritarian, and totalitarian systems [citation:1]. It received the American Political Science Association's award for Outstanding Book in Political Analysis in 1998 and was reissued by the European Consortium for Political Research in 2005 as the inaugural volume in its ECPR Classics series [citation:17]. A contemporary reviewer called it 'a most significant addition to the field of comparative politics' and predicted it would be recognized as 'the leading study of the number, the ideological positioning, and the competitive relations of parties' [citation:8].

Polarized pluralism is Sartori's category for systems with extreme pluralism (six or more relevant parties) and large ideological distance between the extremes [citation:16]. Its distinctive features include: the presence of anti-system parties, bilateral oppositions, occupation of the political center (which pushes competition outward), centrifugal competition, ideological politics, irresponsible opposition, and the politics of outbidding [citation:7][citation:16]. The center is 'out of competition' because it is occupied by a governing party; new parties are driven toward the extremes. This dynamic makes polarized pluralism less stable and less governable than moderate pluralism.