Electoral system
The formal rules and procedures for selecting the executive or members of the legislature
Mandate
The broad support of the people to carry out proposed policies
Runoff election
A second and final election held between the top two vote-getters when no candidate has won the majority
Multimember district system (MMD)
A system for selecting the members of the legislature where 2 or more candidates are elected from a district
Single-member district system (SMD)
A system for electing members of the legislature where the candidate who wins the most votes in a district earns a seat in the legislature
UK
Plurality
The most votes, but not necessarily the majority
First-past-the-post (FPTP)
An election rule in the SMD system where the candidate with a plurality of votes wins a seat
UK, Nigeria (Legislature)
Proportional representation system (PR)
A system for electing members of the legislature where seats are awarded based on the percentage of votes a party receives
Mexico (Legislature), Russia (State Duma)
Mixed electoral system
A system for electing members of the legislature that includes aspects of both the SMD and PR systems
Russia, Iran
One-party system
A country where only one party is allowed to control the government
China
Dominant party system
A party system where multiple parties exist, but one party dominates the executive and wins most of the seats in the legislature
Russia
Two-party system
A party system where only 2 parties are able to garner enough votes to win an election, although more may compete
Multiparty system
A party system where more than 2 parties can win a national election and control the government
Mexico, UK, Nigeria
Catch-all party
A party that takes ideologically diverse positions to capture as many voters as possible
Duverger’s law
A theory that states in political systems with single-member districts and the plurality voting system, two main parties tend to emerge