Party Systems: One, Two, and Many
The different configurations of party competition: dominant party systems, two-party systems, and multi-party systems.
Counting Parties
Party systems are classified by the number of parties that meaningfully compete for power. In a one-party system (China, Cuba), only one party is legally permitted or effectively controls all elections. In a dominant party system (Japan under the LDP 1955-1993, South Africa under the ANC), multiple parties exist but one consistently wins. In a two-party system (the US, historically the UK), two parties dominate and regularly alternate in power. In a multi-party system (the Netherlands, Israel, India), several parties win significant seat shares and coalition government is the norm.
Political scientist Giovanni Sartori refined this classification by considering not just the number of parties but the ideological distance between them and whether competition is centripetal (parties converge toward the center) or centrifugal (parties move toward the extremes). A polarized multi-party system with extremist parties on both ends behaves very differently from a moderate multi-party system where all parties are near the center.