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Choosing our elected representatives is more complex than it looks.
There are an infinite number of electoral systems. Every town, city, state, nation, and group of nations across the world uses a different electoral system.
In this introduction to electoral systems, we describe key concepts in the design of electoral systems, grouped into three areas:
1. The geography of elections
2. The number of winners per contest
3. The logic of choosing winners
When designing an electoral system (or thinking about reform of an existing one), each choice should reflect clear goals, values, and interests. Each choice also has consequences for the character of politics and democracy within a polity.
Elections can happen in a set of districts (with separate contests) that together form a polity or “at large,” with the same contest across the whole polity.
District: Geographical subregions into which a city, county, state, or country is divided for election purposes.
At large: A single contest that takes place across the whole polity, such as a whole city, county, state, or nation.
Take the example of "Dodoville," a small city with a 3-member city council. They are decided whether to elect councilors at large or in districts.
If Dodoville residents use at-large representation:
🦤 All Dodoville councilors represent the whole of the city.
🦤 Every Dodoville resident can vote for all city councilors. Candidates may reside anywhere in Dodoville.
🦤 Ballots are the same throughout Dodoville.
If Dodoville residents adopt district representation:
🦤 Each Dodoville city councilor represents a specific geographic area (district 1, 2, or 3).
🦤 Residents vote for only one of Dodoville's three councilors: the one that represents their district. Candidates must reside in the district.
🦤 Ballots are different in each district.
Executive offices such as mayor or lieutenant governor are usually elected at large, since there is typically only one to elect.
Legislative bodies can be elected by district, at large, or a combination of the two. Choosing between districts and at-large representation depends on whether the polity wants to:
Represent geographically distinct or concentrated constituencies (✅ for districts) or provide representation to groups dispersed across the polity (✅ for at large).
Use multi-winner electorsl systems like proportional representation (✅ for at large, ❌ for districts).
Want to learn more about drawing districts (and "gerrymandering")
A second part of the electoral system to consider is the number of winners elected per contest, technically known as “district magnitude.” Each district or at-large contest can elect one (in “single-winner” contests) or multiple officers (in “multi-winner” contests).
District Magnitude: The number of candidates elected in each contest.
Single Winner: A district or at-large contest in which only one office is elected (district magnitude = 1️⃣). Also known as a “single member” or “single seat.”
Multi Winner: A district or at-large contest in which two or more winners are elected from the same set of candidates (district magnitude = 2️⃣ or more).
Electoral systems can use any combination of single-winner and multi-winner contests.
Executive offices such as mayor or lieutenant governor tend to lend themselves to single-winner contests, since there is typically only one to elect.
Legislative bodies can be elected in single-winner districts, multi-winner districts, or a combination of the two. Choosing between single-winner and multi-winner representation depends on the people's goals.
Strengthen parties as the vehicle of representation
Multi-winner districts are necessarily larger (in population and geography) and weaken the link between constituency and elected representative in favor of political parties.
Elect multiple parties
Legislatures using multi-winner districts, especially ones with proportional representation and high district magnitudes, tend to elect more political parties representing more ideologies and interests.
Require coaltion governance
When combined with proportional representation, these legislatures have more and varied political parties without any one majority party. Coalition governance is common.
Facilitate candidate representation of local constituencies
Single-winner districts allow for smaller constituencies and the districts that represent particular communities. This is why single-winner districts have been used to represent African-American communities under the Voting Rights Act. The flip side of the ability to precisely draw districts and choose voters is the risk of gerrymandering.
Encourage two-party competition
Because there can only be one winner, single-winner districts encourage voters to rally around the candidates of two large political parties, lest they "split the vote" or "waste" their vote on a candidate or party that cannot win. Often called "Duverger's Law,"
Produce exaggerated legislative majorities
The winner of each district is identified in isolation, which means the number of seats won by a political party can be very disproportionate to overall vote cast for that party. A political party will often win a majority of seats in a legislature without winning a majority or even the most votes across the polity.
Want to learn more about "gerrymandering"?
The most common idea is that whichever candidate(s) gets the most votes in a particular contest wins that contest, without any regard for the composition of larger elective body or set of representatives (“plurality”).
Alternatively, a system may demand that the winner wins a majority of votes, either in a particular contest or across the polity, or both. These systems will employ a device (like runoffs or Ranked-choice Voting) to thin the field and manufacture a majority when none exists among the full slate of candidates.
Or an electoral system may seek to achieve representation that is proportional to the vote across the polity. For example, if a party wins 25% of the vote in a country, they should win close to 25% of the seats overall.
Finally, an electoral system may seek to provide diverse or "pluralistic" representation, ensuring some third-party or independent representation in addition to majority or plurality winners.
Winner(s) must get the most votes to win, irrespective of whether (in a single-winner contest) they receive half of more of the votes.
Winner(s) must win a majority (more than half) of the votes to win.
Winners are determined in multi-winner contests in proportion to the aggregate number of votes for each party or candidate.
Uses majority or plurality for most winners, but includes some formula or device to ensure representation of minority and minor parties and/or independent candidates.
In recent years, its is common for observers to highlight that one or other political parties wins more seats in Congress than their national vote share. This is by design. The single-winner plurality and majority systems used in to elect members of Congress are designed to represent the majority or plurality in each district, not provide for proportional outcomes across Congress.
Proportional systems, used in many legislatures around the world, are designed to ensure that seats won more closely match votes cast. Proportional systems can only operate in multi-winner contexts (since it is possible to proportionally assign a single seat). Proportional systems get more proportional the higher the district magnitude.
In plurality and majority systems, a large number (even a majority) of votes do not contribute to election a candidate (their votes are "wasted"). Proportional systems use information from more voters votes to elect a set of candidates in proportion to the overall vote.
Proportional systems represent the idea everyone, not only the supporters of the most popular candidates, deserve representation. However, they also rarely produce single-party majorities, which sometimes results in unstable coalitions of parties organize the legislature (and frequent changes in leadership). Proportional systems also weaken the link between representative and voter, in place of a partisan connection.
Want to learn more about proportional representation?
Our government structure—the Constitution, our electoral laws, the rules and conventions of politics and elections—represent our values and priorities as a people. Increasingly it is understood that government can, and should, be deliberately designed to achieve certain goals and reflect the values we hold dear.
Three key concepts are important for anyone interested in designing a better democracy:
Constitutional engineering: Popularized by political scientist Giovanni Sartori in Comparative Constitutional Engineering (1994), constitutional engineering is the intentional design or reform of a political unit’s constitution and legal structures.
Political engineering: Also involving intentional design and reform, political engineering involves applying political science knowledge to the design or reform of our institutions to achieve specific social, electoral, or governance outcomes.
Constitution-building: This is as a long-term and historical process, in which a polity agrees on the need for change, establishes rules for drafting the new rules, writes the new constitution (using concepts from constitutional and political engineering), gives it legal effect through a ratification process, and implements the new constitution.
Want to learn more about designing democracy?
Donald L. Horowitz (2003) Electoral Systems: A Primer for Decision Makers.
International IDEA (2011) Practical Guide to Constitution Building.
Zim Nwokora (2022) Constitutional Design for Dynamic Democracies.
Giovanni Sartori (1994) Comparative Constitutional Engineering.