Districted Majority with Party-Backfill Proportional Representation

[Brian Langstraat]

Districted Majority with Party-Backfill (DMPB) would be a simple voting system for Proportional Representation (PR).

Overview of DMPB:

Voters vote for a single candidate within their district.

Each candidate with the majority of votes in their district is the winner for that district.

The remaining votes for every candidate without a majority in their district are counted per party and transferred to determine the winner in each district.

Details of DMPB:

1. Voters vote for a single candidate within their district.

1a. All districts are assumed to have equal populations]

2. Each candidate with the majority of votes in their district is the winner for that district.

3. The remaining votes for every candidate without a majority in their district are counted per party.

3a. Non-party/independent/write-in candidates are counted as a single non-party "party".]

4. The party with the most remaining votes transfer votes to their candidate with the most votes from their candidate with the least votes until their candidate with the most votes has the majority of votes in their district (so they are the winner for that district) or they have all of their party's remaining votes.

4a. If parties tie for most remaining votes, then the party with least winners gets to transfer.

4b. Furthermore if parties tie for the number of winners, then the party with the candidate with the most votes gets to transfer.

4c. If candidates within a party tie for the most votes, then the candidate that gets transfer votes is in the district with the top competing candidate with the least votes.

4d. If candidates within a party tie for the least votes, then the candidate that gives transfer votes is in the district with the top competing candidate with the most votes.

4e. Candidates with zero votes are eliminated.

5. When all of the parties have transferred all of their remaining votes, the candidate with the plurality of votes in each district without a winner is the winner for that district.

[Ted Stern]

If I understand this correctly, after each round of transferring votes (step 4), it might be possible for a candidate who won initially in their district to lose.

So what happens then?  Do the candidate's votes then get put into the party pool for transfer to other party candidates?

One might have a situation in which all districts have 51% winners of party A, but party B eventually transfers votes to cause a B victory in the district(s) with their strongest candidates.  So you could have a situation, with, say, 11 seats, in which the weakest 5 winners from party A are replaced by candidates from party B?

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[Brian Langstraat]

Dodecatheon,

Districted Majority with Party-Backfill (DMPB), as I detailed it, has several issues, but pretty much the opposite of your understanding.

If all districts have 51% winners from party A, then party B would not be able to transfers remaining votes.

Also, all winners could only use a slight majority (~51%) of the votes for the major (2 or 3) parties and the slight minority (~49%) of the votes for minor parties/independents would be wasted.

Thus, DMPB would heavily favor district majority over proportionality.

How you understood DMPB may actually produce a (better) voting method that favors proportionality over the district majority: Districted Party-Backfill (DPB)

Overview of DPB:

Voters vote for a single candidate within their district.

The candidate(s) with the most votes receive transferred votes from the candidate(s) within their party with the least votes to determine winners

Details of DPB:

1. Voters vote for a single candidate within their district.

2. Each candidate with all of the votes in their district is the winner for that district.

2a. The votes for losing candidates will be transferred to other candidates in their party.

2b. Non-party/independent/write-in candidates are counted as a single non-party "party".

3. Repeatedly, the candidate with the most (non-winning, overall) votes receives transferred votes within their party from (primarily) a losing candidate or (secondarily) the candidate with the least votes until the candidate with the most votes has votes equal to the number of votes in their district (so they are the winner for that district) or they have all of their party's remaining votes.

3a. If candidates tie for the most votes, then the candidate that gets transfer votes is in the district with the top competing candidate with the least votes.

3b. If candidates within a party tie for the least votes, then the candidate that gives transfer votes is in the district with the top competing candidate with the most votes.

3c. Candidates with zero votes are eliminated.

4. When all of the parties have transferred all of their remaining votes, the candidate with the most votes in each district without a winner is the winner for that district.

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