4.2 Party Systems

What is a Party System?

A party system describes the number and relative strength of political parties competing for power in a country. The three main types studied are dominant-party, two-party, and multi-party systems. The number of viable parties shapes coalition-building, representation, and stability of governance.

Dominant-Party vs. Two-Party Systems

In a dominant-party system, one party consistently wins power despite other parties existing and competing (e.g., China's CCP, historically Mexico's PRI). In a two-party system, like the UK or Nigeria, two major parties dominate, often producing stable single-party majority governments due to plurality (SMD) electoral rules.

Multi-Party Systems and Coalitions

Multi-party systems, common in countries using proportional representation (PR) like Mexico and Iran (to a degree), feature several viable parties, often requiring coalition governments. This can increase representation of diverse views but may cause instability, slower policymaking, or gridlock if coalitions collapse.

Key terms

Party System

The number and relative strength of parties competing for power within a country.

Dominant-Party System

A system where one party wins consistently despite other parties legally competing (e.g., Mexico's PRI historically).

Two-Party System

A system where two major parties dominate elections and government, often linked to SMD plurality rules (e.g., UK).

Multi-Party System

A system with several viable parties, often requiring coalition governments; common with PR electoral rules.

Coalition Government

A government formed when multiple parties combine to create a governing majority, common in multi-party systems.

Try an AP-style question

Which course country has a dominant-party system?

1. Russia
2. Nigeria since 2015
3. Mexico after 2000
4. United Kingdom