The electoral threshold, or election threshold, is the minimum share of the primary vote which a candidate or political party requires to achieve before they become entitled to any representation in a legislature. This limit can operate in various ways. For example, in party-list proportional representation systems an electoral threshold requires that a party must receive a specified minimum percentage of votes (e.g. 5%), either nationally or in a particular electoral district, to obtain any seats in the legislature. In multi-member constituencies using preferential voting, besides the electoral threshold, to be awarded a seat, a candidate is also required to achieve a quota, either on the primary vote or after distribution of preferences, which depends on the number of members to be returned from a constituency.
The effect of an electoral threshold is to deny representation to small parties or to force them into coalitions, with the presumption of rendering the election system more stable by keeping out fringe parties. Proponents note that simply having a few seats in a legislature can significantly boost the profile of a fringe party; and that providing representation and possibly veto power for a party that, say, receives only 1% of the vote, may not be appropriate. However, critics argue out that in the absence of a ranked ballot system, supporters of minor parties are effectively disenfranchised and denied the right of representation by someone of their choosing.
Two boundaries can be defined—a threshold of representation is the minimum vote share that might yield a party a seat (under the most favorable circumstances for the party) while the threshold of exclusion is the maximum vote share that could be insufficient to yield a seat (under the least favorable circumstances). Lijphart suggested calculating the informal threshold as the mean of these.