Single-member district

It has been argued by proponents of single-member constituencies that it encourages a stronger connection between the representative and constituents and increases accountability and is a check on incompetence and corruption. In countries that have multi-member constituencies, it is argued that the constituency link is lost. For example, in Israel the whole country is a single constituency and representatives are selected by party-lists.

On the other hand, today most voters tend to vote for a candidate because they are endorsed by a particular political party or because they are in favor of who would become or remain the leader of the government, more than their feelings for or against the actual candidate standing. Sometimes voters are in favor of a political party but do not like specific candidates. For example, voters in Canada re-elected the Alberta government in 1989 but, because of dissatisfaction with its leadership, the premier and leader of the governing party, Don Getty, lost his seat.

It has been argued that single-member districts tend to promote two-party systems (with some regional parties). Called Duverger's law, this principle has also been empirically supported by the cube rule, which shows how the winning party in a first-past-the-post system is mathematically over-represented in the legislature. For example, in the 2014 United States House of Representatives elections, the Republican Party won 51.2% of the popular vote but 56.7% of the seats.

Supporters view this effect as beneficial, claiming that two-party systems are more stable, and that the minority opposition does not have undue power to break a coalition. First-past-the-post minimizes the influence of third parties and thus arguably keeps out forms of opposition outside of the dominant rival party. Critics of two-party systems believe that two-party systems offer less choice to voters, create an exaggerated emphasis on issues that dominate more marginal seats, and does not completely remove the possibility of a balanced chamber (or hung parliament), which can also give undue power to independents and lead to more, not less, stability.

A safe seat is one in which a plurality or majority of voters, depending on the electoral system, support a particular candidate or party so strongly that the candidate's election is practically guaranteed in advance of the vote. This means votes for other candidates effectively make no difference to the result. This results in feelings of disenfranchisement, as well as increased nonparticipation, by both supporters of the dominant candidate (who can confidently abstain from voting because their preferred candidate's victory is nearly assured) as well as supporters of other candidates (who know their preferred candidate is essentially guaranteed to lose).[5]

Single-member districts enable gerrymandering, the practice of manipulating district boundaries to favor one political party.[6][7] Whereas proportional multi-member districts ensure that political parties are represented roughly in proportion to the share of the vote they receive, in single-member districts the entire district is represented by a single politician, even if a sizeable minority (or even a majority, in the case of plurality voting) of the electorate votes for candidates from other parties. This enables political parties to rig elections in their favor by drawing districts in such a way that more districts are won by their party than their proportion of the overall vote would dictate (in the 2018 Wisconsin State Assembly election, for example, the Republican Party won 45% of the popular vote but 64% of the seats, due in part to gerrymandering[8]).[9]

Contrary to conventional wisdom, a 2023 study found that single-member district systems do not have more geographically representative parliaments than systems with multi-member districts.[10]