State legislative chambers that use multi-member districts
There are two other electoral systems employed in the United States, single-member and at-large. At-large districts are only used currently for the U.S. House of Representatives in states that are only allotted one representative. The vast majority use single-member districts at both the federal and state levels.
Per Loyola law professor Justin Levitt, Arizona, New Jersey, South Dakota, and Washington use MMDs to elect all state House members; 10 other states allow the use of MMDs by law even when not used; and five states are legally neutral on the matter.
According to the Vermont Legislative Research Service, there are five forms of MMD:
- 1. Bloc: free-for-all - voters receive as many votes as there are open seats, and can vote once for a particular candidate. All votes must be used.
- 2. Bloc with partial abstention: Same as bloc, except voters can elect not to use all of their votes.
- 3. Cumulative: Voters are free to use their votes however they wish. This is not used in state legislative elections at present; in 1982, Illinois was the last state to abandon the system.
- 4. Staggered: Two legislators represent the same district with elections happening in different years.
- 5. Seat/post: Instead of running in a pool of candidates with the aim of finishing strongly enough, candidates run for a specific seat as in a single-member district.
Forms can be mixed; bloc voting can occur in a post election, and districts can vary in a state.
Floterial districts are otherwise separate districts that geographically overlap each other, giving the effect of a multi-member district in the area of overlap. These are allowed in New Hampshire.
States currently employing MMDs
|State Senate||House of Representatives||Range of members after the 2012 elections|
|Arizona||Bloc with partial abstention||2|
|South Dakota||Bloc/Post||2 (some districts 2 posts)|
|Vermont||Bloc||Bloc||House: 1-2 |
|Washington||Post||2 (2 posts per district)|
|West Virginia||Staggered||Bloc||Senate: 2 |
Nearly all MMD states have constitutional prescriptions for their use:
- New Hampshire
- New Jersey
- North Dakota
- South Dakota
- West Virginia
The senate shall be composed of one member elected from each of the thirty legislative districts established pursuant to this section. The house of representatives shall be composed of two members elected from each of the thirty legislative districts established pursuant to this section.
A senatorial or representative district, when more than one county shall constitute the same, shall be composed of contiguous counties, and a county may be divided in creating districts only to the extent it is reasonably determined by statute that counties must be divided to create senatorial and representative districts which comply with the constitution of the United States. A county may be divided into more than one legislative district when districts are wholly contained within a single county. No floterial district shall be created. Multi-member districts may be created in any district composed of more than one county only to the extent that two representatives may be elected from a district from which one senator is elected. The provisions of this section shall apply to any apportionment adopted following the 1990 decennial census.
The State shall be divided by law into legislative districts for the election of members of the Senate and the House of Delegates. Each legislative district shall contain one (1) Senator and three (3) Delegates. Nothing herein shall prohibit the subdivision of any one or more of the legislative districts for the purpose of electing members of the House of Delegates into three (3) single-member delegate districts or one (1) single-member delegate district and one (1) multi-member delegate district.
As soon as possible after the convening of the next regular session of the legislature, and at the session in 1971, and every ten years thereafter, the legislature shall make an apportionment of representatives according to the last general census of the inhabitants of the state taken by authority of the United States or of this state. In making such apportionment, no town, ward or place shall be divided nor the boundaries thereof altered.
When the population of any town or ward, according to the last federal census, is within a reasonable deviation from the ideal population for one or more representative seats, the town or ward shall have its own district of one or more representative seats. The apportionment shall not deny any other town or ward membership in on non-floterial representative district. When any town, ward, or unincorporated place has fewer than the number of inhabitants necessary to entitle it to one representative, the legislature shall form those towns, wards, or unincorporated places into representative districts which contain a sufficient number of inhabitants to entitle each district so formed to one or more representatives for the entire district. In forming the districts, the boundaries of towns, wards, and unincorporated places shall be preserved and contiguous. The excess number of inhabitants of district may be added to the excess number of inhabitants of other districts to form at-large or floterial districts conforming to acceptable deviations. The legislature shall form the representative districts at the regular session following every decennial federal census.
4. Two members of the General Assembly shall be elected by the legally qualified voters of each Assembly district for terms beginning at noon of the second Tuesday in January next following their election and ending at noon of the second Tuesday in January two years thereafter.
A senator and at least two representatives must be apportioned to each senatorial district and be elected at large or from subdistricts from those districts. The legislative assembly may combine two senatorial districts only when a single member senatorial district includes a federal facility or federal installation, containing over two-thirds of the population of a single member senatorial district, and may provide for the election of senators at large and representatives at large or from subdistricts from those districts.
The Legislature shall apportion its membership by dividing the state into as many single-member, legislative districts as there are state senators. House districts shall be established wholly within senatorial districts and shall be either single-member or dual-member districts as the Legislature shall determine.
The House of Representatives shall be composed of one hundred fifty Representatives. The voters of each representative district established by law shall elect one or two Representatives from that district, the number from each district to be established by the General Assembly.
The Senate shall be composed of thirty Senators to be of the senatorial district from which they are elected. The voters of each senatorial district established by law shall elect one or more Senators from that district, the number from each district to be established by the General Assembly.
Washington's House MMDs are prescribed by statute:
"The house of representatives shall consist of ninety-eight members, two of whom shall be elected from and run at large within each legislative district."
For the election of senators, the state shall be divided into twelve senatorial districts, which number shall not be diminished, but may be increased as hereinafter provided. Every district shall elect two senators, but, where the district is composed of more than one county, both shall not be chosen from the same county.
After every census the delegates shall be apportioned as follows: The ratio of representation for the House of Delegates shall be ascertained by dividing the whole population of the state by the number of which the House is to consist and rejecting the fraction of a unit, if any, resulting from such division. Dividing the population of every delegate district, and of every county not included in a delegate district, by the ratio thus ascertained, there shall be assigned to each a number of delegates equal to the quotient obtained by this division, excluding the fractional remainder. The additional delegates necessary to make up the number of which the House is to consist, shall then be assigned to those delegate districts, and counties not included in a delegate district, which would otherwise have the largest fractions unrepresented; but every delegate district and county not included in a delegate district, shall be entitled to at least one delegate.
The Constitution does not specify the method of apportionment for federal representatives. This led most of the original thirteen states to employ multi-member districts in the first congressional elections. By 1842, six states were electing U.S. Representatives at-large, though three only had one representative. Congress established single-member districts that year in a landmark apportionment act; MMDs have not been seen in the U.S. House since. Each state continues to elect two U.S. Senators at-large on staggered schedules.
Decline in the state legislatures
- See: Legal issues
Even as the legislative branch of the federal government eschewed MMDs, they continued to be a popular form of electing state legislators up until the mid-20th century.
As the civil rights movement took hold in the 1960s, it became apparent that MMDs put racial and partisan minorities at a significant disadvantage at the voting booth, as the majority could simply outvote them even when they could prevail in their own single-member district. By states' own volition as well as court decisions, MMDs' usage began to decline from nearly half of legislative seats at the turn of the 1960s to 26 percent of representatives and 7.5 percent of senators in 1984. By 1998, the number of states with MMDs had fallen to 13.
Hawaii considers return
Hawaii changed to single-member districts in 1982 after a district court found the state's reapportionment plan unconstitutional in Travis v. King. Gov. Neil Abercrombie -- who some have suggested benefited from MMDs early in his political career- suggested that voters decide on a constitutional amendment reinstating multi-member districts. Though the Attorney General cleared MMDs, the state's reapportionment commission voted to reject reviving MMDs in June 2011, putting the issue to rest for at least another decade.
In 2006, New Hampshire voters approved a constitutional amendment that gave each town with a sufficient population its own representative. This provided for floterial districts, which -- in a state already using MMDs -- allowed for even more representation.
West Virginia considers change
In 2011, West Virginia had 22 MMDs ranging from two to seven members. This led to a debate over whether to abandon the system for single member. While MMDs were kept after redistricting, the highest number of delegates in a given district was reduced to five.
Nevada eliminates Senate MMDs
Effects on incumbents
Studies differ over whether incumbents are more likely to face defeat in MMDs. 
Effects on female and minority representatives
Female legislators have repeatedly been shown to be more numerous in MMDs. The relation of MMDs to minority legislators is far less clear, though.
- Redrawing of boundaries not necessary, as the number of members can simply be adjusted
- Stands to increase ideological diversity, encourage third-party candidates
- More time spent on constituent service 
- Harder to build cohesion
- Harder to hold individual members accountable
- Plunking -- the act of voting for only one candidate -- can work to the benefit of a party or interest group. 
- No direct connection between member and voter as with the single-member system
- Possibly violates the principle of 'one man, one vote'
- Occasionally conflicts with Voting Rights Act regulations
- More expensive to run
The U.S. Supreme Court has discouraged the use of multi-member districts over time, but has not entirely ruled them unconstitutional. While they are legally acceptable in drawing state legislative boundaries (though not preferable in court-ordered reapportionment per Connor v. Johnson), federal law dating back to 1842 dictates that they cannot be used in drawing boundaries for the U.S. House of Representatives. By the time the last law requiring single-member districts was passed in 1967, Hawaii and New Mexico were the only states left to be affected.  
Equal Protection Clause
Fortson v. Dorsey
In 1965, the Supreme Court ruled that the Equal Protection Clause does not necessarily require all legislative districts to be single-member.
Burns v. Richardson
The following year, the Court ruled that there was no requirement that one state chamber be single-member.
White v. Regester
In 1973, a case from Texas went to the Supreme Court, who ruled that MMDs could not be used to disenfranchise racial groups.
City of Mobile v. Bolden
In 1980, the court ruled that to violate the Equal Protection Clause, the discriminatory entity must have had a purpose for doing so, and a matching result must have manifested from it.
Voting Rights Act amendments of 1982
Prior to 1982, legal challenges to multi-member districts were based on either the Fourteenth Amendment (known as the Equal Protection Clause) or the Fifteenth Amendment (the equal right of citizens to vote). Congress moved to amend the Voting Rights Act that year, practically overturning the decision in Bolden. This meant that courts could overturn MMDs based on the effect on minority voters without requiring proof of discriminatory intent.
Thornburg v. Gingles
In 1986, the high court overturned North Carolina's multi-member districts on grounds of discrimination against black voters. Tim Storey of the National Conference of State Legislatures credits the case with the sudden drop in MMDs from the 1970s to the 1980s, even though the decision did not limit MMDs in other states.
- Chapter on MMDs from NCSL report on redistricting
- Vermont Legislative Research Service report on MMDs
- Article on single-member districts' rise
- Research paper on MMD effects on women/minorities
- ↑ 1.0 1.1 National Council on State Legislatures, "Declining Use of Multi-Member Districts," July 13, 2011. Retrieved July 25, 2012.
- ↑ 2.0 2.1 National Council on State Legislatures, "Changes in Legislatures Using Multimember Districts after Redistricting," September 11, 2012. Retrieved December 12, 2012.
- ↑ 3.0 3.1 Loyola Law School, "Where are the lines drawn?" Retrieved July 23, 2012.
- ↑ 4.0 4.1 4.2 Vermont Legislative Research Service, "The Pros and Cons of Multi-Member Districts," retrieved July 25, 2012
- ↑ 5.0 5.1 West North Carolina Library Network, "The Mismeasure of MMD: Reassessing the Impact of Multi Member Districts on Descriptive Representation in U.S. State Legislatures" by Lilliard Richardson and Christopher Cooper, retrieved July 25, 2012.
- ↑ 6.0 6.1 The Georgia Political Economy Group, School of Public and International Affairs, The University of Georgia, "Ideological Extremism, Branding, and Electoral Design: Multimember versus Single Member Districts" by Anthony Bertelli and Lilliard Richardson, November 10, 2006. Retrieved July 25, 2012.
- ↑ Washington State Legislature, Revised Code of Washington Title 44.05.090, retrieved July 16, 2012.
- ↑ FairVote, "A History of One Winner Districts for Congress" by Nicolas Flores, retrieved July 25, 2012.
- ↑ 9.0 9.1 FairVote, "History of Single Member Districts for Congress" by Tory Mast, retrieved July 25, 2012
- ↑ 10.0 10.1 Redistricting Task Force for the National Conference of State Legislatures archived by the Minnesota State Senate, "Multimember Districts," retrieved July 25, 2012.
- ↑ 11.0 11.1 Honululu Star-Advertiser, "Multimember districts being talked up again," May 13, 2011. Retrieved July 25, 2012
- ↑ Honululu Star-Advertiser, "Multimember districts OK, redistricting panel told," June 9, 2011. Retrieved July 25, 2012
- ↑ Honululu Star-Advertiser, "Multimember districts rejected," June 10, 2011. Retrieved July 25, 2012
- ↑ Hawaii Business, "Should Hawaii Keep its Singlemember Legislative Districts?" Retrieved July 25, 2012.
- ↑ West Virginia MetroNews, "States Trend Toward Single-Member Districts, Policy Expert Says," July 13, 2011. Retrieved July 25, 2012.
- ↑ 16.0 16.1 ACE project, "Multimember Districts," retrieved July 25, 2012.
- ↑ 17.0 17.1 Governing, "The Disappearance of Multi-Member Constituencies," July 7, 2011. Retrieved July 25, 2012.
- ↑  The Leadership Conference, "History of the VRA, Retrieved July 25, 2012.]
- ↑ U.S. Supreme Court, Thornburg v. Gingles, 478 U.S. 30 (1986)