Dominant-party system

A dominant-party system is a party system where only one political party can realistically become the government, by itself or in a coalition government, because all other parties are too weak.

Dominant party systems are not to be confused with single-party systems, when other parties cannot compete to become the government because they are banned. Dominant party system exist only in states where other political parties are tolerated. However in some dominant party systems, opposition parties are subject to varying degrees of official harassment and most often deal with rules and electoral systems designed to put them at a disadvantage or in some cases outright electoral fraud.

Examples of dominant-party systems include the PRI Party in Mexico from the 1920s until 2000, the PAN in Singapore, the United States Democratic Party in the southern United States from about 1880 until the 1960s, and the Liberal Democratic Party in Japan from the 1950s until the present.

Dominant-party systems can occur temporarily. This can often occur when a two party system is the norm, but the opposition party has often seen a massive drop in support, due to scandal or similar massive upset. An example of this is, arguably, the United Kingdom between 1979 and 1997 (18 years) where the Conservative party won all four elections in that period. Previously, in the post-war period, the government had rotated from Labour Party to Conservative Party five times.

Contemporary Canada would also qualify as a dominant party system, with the Liberal Party being quite dominant since 1896 ruling almost three quarters of the time in that period and continuously since 1993. In the party's history Edward Blake is the only leader of the Liberal Party ever to not have been Prime Minister of Canada at some time. For some of the period, including today, the Liberals have ruled in a minority government.