Multi-member system

Multi member voting methods, also called multi winner methods, are voting methods which elect multiple people in one election. It is common for several of these voting methods to be combined into a Regional System.

Bloc voting methods

Bloc methods find the candidate set with the most support or the most votes overall using the same metric which would be used in a single member system. The number of seats up for election is determined and the top candidates are elected to fill those seats.

Common examples:

• Bloc Approval Voting: Each voter chooses (no ranking) as many candidates as desired. Only one vote is allowed per candidate. Voters may not vote more than once for any one candidate. Add all the votes. Elect the candidates with the most votes until all positions are filled.
• Bloc Score Voting: Each voter scores all the candidates on a scale with three or more units. Starting the scale at zero is preferable. Add all the scores. Elect the candidates with the highest total score until all positions are filled.
• Bloc STAR Voting: Each voter scores all the candidates on a scale from 0–5. All the scores are added and the two highest scoring candidates advance to an automatic runoff. The finalist who was preferred by (scored higher by) more voters wins the first seat. The next two highest scoring candidates then runoff, with the finalist preferred by more voters winning the next seat. This process continues until all positions are filled.
• Cumulative voting: In this system, a voter facing multiple choices is given X number of points. The voter can then assign his points to one or more of the choices, thus enabling one to weight one's vote if desired. This could be achieved through a normalized ratings ballot, or through multiple plurality ballots, one per each point allocated. Typically, each voter will have as many votes as there are winners to be selected.
• Single non-transferable vote: Each voter casts one vote for one candidate in a multi-candidate race for multiple offices
• Bloc Plurality Voting: Each voter chooses as many candidates as there are seats to be elected. Add all the votes. Elect the candidates with the most votes until all positions are filled.

Sequential proportional methods

Sequential Cardinal Methods elect winners one at a time in sequence using a candidate selection method and a reweighting mechanism. The single-winner version of the selection is applied to find the first winner, then a reweighting is applied before the selection of the next and subsequent winners. A reweighting is applied to either the ballot or the scores for the ballot itself. The purpose of the reweighting phase is to ensure outcomes have a high level of Proportional representation by requiring them to satisfy criteria like the Hare Quota Criterion.

Common examples:

• Sequential proportional approval voting
• Reweighted Range Voting
• Sequential Monroe voting
• Allocated Score
• Sequentially Spent Score
• Single transferable vote
• Single distributed vote
• Sequential Ebert

Optimal proportional methods

Optimal Systems select all winners at once by optimizing a specific desirable metric for proportionality. First a "quality function" or desired outcome is determined, and then an algorithm is used to determine the winner set that best maximizes that outcome. In most systems this is done by permuting to all possible winner sets not a maximization algorithm. This makes such systems computationally expensive.

Optimal ordinal methods may either be based on weighted positional methods, like Monroe's method, or extend the notion of a Condorcet winner to a winning set, like Schulze STV.

Common examples:

• CPO-STV
• Schulze STV
• Harmonic Voting
• Proportional approval voting
• Phragmén's Method
• Monroe's method
• Ebert's Method
• Max Phragmen
• PAMSAC

Local district clusters vs multi-member districts

Local District Clusters offer an alternative to running a multi-winner voting method in a Multi-Member District. Traditional multi-member districts take single-member districts and combine them, with all candidates elected at-large. In contrast, Local District Clusters link districts into a multi-member cluster which runs a single election, but then elects only one candidate from each district.

For example: In a five winner election, five single-member districts would be linked into a cluster. As usual, most major parties could still be expected to run five candidates. In this “Local” system, each candidate would be elected to a specific single-member district inside their cluster. Using votes from the cluster's full electorate, the first winner would be selected and would be designated as the winner in their home district. All other candidates running in that district would then be eliminated, and the selection rounds would continue until all the seats have been filled and until each district has a designated representative.

All multi-winner voting methods, including multi-member and proportional methods, can be adapted to run in local clusters. The purported inventor of this alternative is Byron Becker for his Local PR system. Although, it is unclear if Fair majority voting which also uses Local District Clusters predates Local PR system or not.

Pros

• Improved Proportionate representation: Once elected, each elected representative is responsible for a smaller area, and can focus on the specific issues important to the citizens of that district.
• Improved Petitioner Accountability: Each voter in each district has a specific representative for local issues who they can hold accountable for local issues such as traffic, schools, hospitals, etc. For issues where a voters local representative doesn't align with them, voters could go to the elected official or officials in their cluster who they voted for partisan or issue based representation. Candidates who fail to deliver on promises, either to their district or to their larger supporter base across the cluster would be easier to vote out, assuming that their supporter base or local electorate wasn't satisfied by their record.

Cons

All the "best" candidates may be running in one district, and when a winner in that district's representative is represented, the other candidates in that district can not win elsewhere. For partisan implementations, political parties would have to take into account strategic nomination considerations to decide who to run in what district.