Electoral System Glossary

A bloc method is a multi-winner voting method classification. It’s the opposite of proportional. Under this method, if a “bloc” of voters greater than 50% all vote the same way, then that bloc can determine all the seats.

A cardinal method is any voting method that allows voters to score their choices along a scale of at least two units. Voters may give equal scores to different choices.

A closed partisan primary is a primary where voters must choose within the party in which the voter is registered. Each party advances the candidate within its party that was chosen the most.

A multi-winner method is any voting method that selects more than one winner.

A nonpartisan primary is a primary where a determined number of candidates move onto the general election without regard to political party. Nonpartisan primaries are always open so that all voters voters may choose among all the candidates regardless of party.

An open partisan primary is a primary where voters may choose within the the one party of their choosing regardless of the voter’s own party affiliation. Each party advances the candidate within its party that was chosen the most.  Note: This type of primary was determined to be unconstitutional in the US; See: California Democratic Party v. Jones.

A parliamentary system means that the governing body, a parliament, elects its prime minister. This is as opposed to the public electing a president. A parliamentary system is unrelated to whether the voting method used is proportional.

A partisan primary is a primary where each political party receives a nominee that moves to the general election.

A plurality-based voting method is a voting method that utilizes plurality voting.

A preferential voting method is any voting method that allows voters to rank at least two choices. These methods typically require voters to not rank any choice equally.

A primary is a preliminary election used to narrow down the candidate pool for a later round. The later round is called the general election.

A proportional voting method is a multi-winner voting method classification. It gives outcomes that are proportionately responsive to the selections that voters give. For example, if a 30% bloc of voters supports an ideology, then roughly 30% of the winners will have that ideology.

A semi-open/semi-closed partisan primary is a primary where voters may choose within one party of the voter’s choosing but only if the party allows them. Any party may choose to limit voters to vote within their party only if they are registered, or the party may choose to allow voters registered under another party or no party to vote within their party. Each party advances the candidate within its party that was chosen the most.

A semi-proportional method is a multi-winner voting method classification. It gives outcomes between bloc and proportional. Semi-proportional methods tend to be more proportional as the number of winners increases.

A single-winner method is any voting method that selects one winner. Some political positions are inherently single-winner like mayor, governor, or president.

A top-two primary is a primary where voters may choose any one candidate, regardless of party. The top two candidates selected the most, regardless of party, move onto the general election. Some top-two primaries declare a winner immediately if a candidate receives greater than 50% of the primary vote.

A winner-take-all election chooses just one winner. In practice, winner-take-all elections typically refer to positions that could be conducted as a multi-winner election. But instead the elections are conducted as a single-winner election where the candidates are associated with a smaller geography. This decision to use a winner-take-all election rules out the ability to use a proportional or semi-proportional method.

Bayesian regret is a utility value output produced through simulated elections. This approach creates a quantitative measure of voter satisfaction while comparing different voting methods. The simulation allows simultaneous interactions of other variables such as tactical voting, voter ignorance, and number of issues.

The Condorcet criterion is satisfied if when a candidate can beat every other candidate in a head-to-head election, that beat-all candidate always wins.

A voting method criterion refers to whether a voting method can behave in a certain undesirable way. If the method can’t ever behave in the undesirable way, then it is said to pass that criterion. But if it can behave in the undesirable way in any circumstance, then the method fails that criterion. This failure is recognized regardless of the undesirable behavior’s degree or frequency.

The favorite betrayal criterion is satisfied if a voter’s ballot always benefits by showing the greatest support for a favorite candidate.

The independence of clones criterion is satisfied if an otherwise winning candidate is not caused to lose by introducing an identical candidate.

IIA is satisfied if adding an additional non-winning candidate can never change the winner.

The later-no-harm criterion is satisfied if a voter cannot cause a more preferred candidate to lose by giving an additional ranking or positive rating to a less preferred candidate.

The majority criterion is satisfied if when more than half of voters prefer a candidate, that (absolute) majority candidate always wins.

The monotonicity criterion is satisfied if (1) giving greater support for a candidate can never hurt that candidate, and (2) giving less support for a candidate can never benefit that candidate.

The majority criterion is satisfied if when more than half of voters prefer a candidate, voters can always strategically vote so that (absolute) majority candidate wins.