Dominant-party system

A dominant party governs alone or as the senior partner for a long run of elections while other parties are legal and compete. The category spans regimes: in some, the party wins fair contests against a weak opposition; in others, it wins because it controls the state, the media and the resources opponents need.

Giovanni Sartori (1976) described a 'predominant-party system' as one in which the same party wins an absolute majority of seats over several consecutive elections under genuine competition, and distinguished it from a 'hegemonic' system, where other parties exist only as satellites. T. J. Pempel's Uncommon Democracies (1990) compared democratic cases such as Japan, Sweden, Israel and Italy. For authoritarian cases, Beatriz Magaloni (2006) argued that Mexico's PRI survived by making millions of voters dependent on its patronage and punishing defection, and Kenneth Greene (2007) that dominant parties turn public resources into patronage to bias competition, so that they 'virtually win elections before election day' without massive fraud. When the economic basis of dominance erodes, for instance through privatisation, the playing field levels and opposition parties can grow.

• Mexico: the PRI and its predecessors held the presidency from 1929 until losing in 2000.
• Japan: the Liberal Democratic Party governed continuously from 1955 to 1993, and for most years since.
• Botswana: the Botswana Democratic Party governed from independence in 1966 until it lost the October 2024 general election to the Umbrella for Democratic Change, which won 36 seats.
• Singapore: the People's Action Party has won every general election since 1959.
• South Africa: the ANC won every national election from 1994 until it lost its majority in 2024.

The boundary between a democratic dominant party and an electoral autocracy is contested and depends on how unfair the playing field is, which is hard to measure. Long dominance can breed clientelism and corruption even where elections are clean, while defenders credit some dominant parties with stability and long-term policy.

Dominant parties do lose: Mexico's PRI in 2000, Botswana's BDP in 2024 and Senegal's Socialist Party in 2000 all accepted defeat. Research suggests that the end of rents and patronage, splits in the ruling party and opposition coordination are the usual paths to turnover.