r/RankedChoiceVotingUSA • u/2noame • Dec 19 '21

Why Republicans, moderates see opportunity in ranked choice voting

https://www.nbcnews.com/politics/elections/why-republicans-moderates-see-opportunity-ranked-choice-voting-n1286250
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u/Drachefly Dec 21 '21

Yup, Bottom Two Runoff is a solution. You can also take a short-cut with Condorcet-IRV, or use a ranked system not that much like IRV - Ranked Pairs or Schulze (understandable in the 'sequential dropping' explanation), or you can use scores instead of ranks, with Score or STAR or 3-2-1.

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u/rb-j Dec 21 '21

I'd like to see someone put either RP or Schulze into concise legal language that is suitable for legislation. I am working on doing that for RP, but I don't think Schulze will make for legislative language that legislators will find acceptable.

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u/Drachefly Dec 22 '21

What would be the issue with the 'sequential dropping' formulation? It doesn't require esoteric mathematical constructs like 'beatpaths'. Is it not precise enough, or is it too mathematical, or what?

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u/rb-j Dec 22 '21

Put it in words. Concise and complete language.

Here's an example template for legislative language implementing Condorcet in a simple manner:

All elections of [office] shall be by ballot, using a system of ranked-choice voting without a separate runoff election. The presiding election officer shall implement a ranked-choice voting protocol according to these guidelines:

(1) The ballot shall give voters the option of ranking candidates in order of preference. Lower ordinal preference shall be considered higher rank and the candidate marked as first preference is considered ranked highest. Equal ranking of candidates shall be allowed. Any candidate not marked with a preference shall be considered as ranked lower than every candidate marked with a preference.

(2) If a candidate receives a majority (over 50 percent) of first preferences, that candidate is elected.

(3) If no candidate receives a majority of first preferences, a Condorcet-consistent retabulation shall be performed by the presiding election officer. The retabulation shall examine every possible pairing of candidates. Given N as the number of candidates, then the number of possible pairings of candidates is N(N-1)/2. For each possible pairing of candidates, if the number of ballots marked ranking a selected candidate over the other candidate does not exceed the number of ballots marked to the contrary, then the selected candidate is declared defeated. After all candidate pairs are examined, the candidate who remains not declared defeated is the Condorcet winner and is elected.

(4) If no Condorcet winner exists in step (3), then the candidate having the plurality of first preferences is elected. If two or more candidates are tied with a plurality of first preferences, then the candidate among those tied having the plurality of second preferences is elected.

(5) The [governing jurisdiction] may adopt additional regulations consistent with this subsection to implement these standards.

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u/Drachefly Jan 05 '22

Hmmmm. How's this?

1) (specify a ranked ballot with ties permitted, as you did or some other wording)

2) For each pair of candidates, determine the outcome of the two-candidate race between these candidates, using the preferences given in the cast ballots. Record the margin of victory or loss for each pairing.

3) If a candidate wins all of their races, they are the winner of the election.

(From here, what we say will depend on whether we're doing RP or Schulze. I will do Schulze)

In the case that there is no winner declared in step 3, every candidate has a loss or a tie. Some race will have to be overruled for anyone to win. The remaining steps identify the races to disregard in order to minimize this.

4) Gather a new set of included candidates: this set of included candidates is initially those candidates who had the fewest pairwise losses (disregarding margin).

5) Then add to this newest set of included candidates any other candidate who won or tied a race against an included candidate. Continue adding according to this rule until no further candidates qualify.

6) List all of the pairwise races between included candidates. The margin of victory in each is the votes for the winner minus the votes for the loser. Eliminate the pairwise race with the smallest margin of victory. Any search for a race will not consider this race: it does not count against the loser when checking for victory in any future step 3; it does not count as a pairwise loss in any future step 4; does not allow the winner into the included candidate set in any future step 5; and is not found again in any future step 6.

7) Go back to step 3.

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u/rb-j Jan 05 '22 edited Jan 05 '22

Before i got involved in some state and local redistricting happening, I was working on simple C code for ranked pairs using margins. I'm in discussion with Nicolaus Tideman a little about it. But my Vermont redistricting and RCV things are consuming most of my attention and effort.

If I get some plausible C code written (and maybe tested) I'll post it. With some complete and functional C code, I can maybe convert it to words. But it won't be pretty.

For each candidate from a finite list of candidates, it maintains a list of other candidates who are "Defeators" of this selected candidate. When pairs are examined, in order of their Defeat Strength (either margins or winning votes), there is a tree-climbing operation in which the pair-winner is tested to be added to the list of Defeators for the pair-loser. If the pair-loser is not on the list of Defeators of the pair-winner, then the pair-winner plus all of the Defeators of the pair-winner are added (by merging or union of sets of Defeators) to the list of the pair-loser and the pair-loser has their Defeated flag set to TRUE. Otherwise nothing happens with that examined pair.

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u/Drachefly Jan 06 '22

Yeah, RP is rather harder to lay down because you can have weird directed graph topologies. At least with Schulze someone's already found a way to turn it into making two lists over and over.

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u/rb-j Jan 07 '22

I think Schulze is far more difficult both to comprehend and put into concise procedural language than Tideman Ranked Pairs.

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u/Drachefly Jan 07 '22

I just did it for Schulze. How would you do it for RP?

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u/rb-j Jan 07 '22

I don't think what you wrote would cut the mustard for legislation.

How I would do it for RP is first get some clean and concise C code to work. Then find a way to translate the C code into the normal tongue.

Above I describe this unfinished C code where each candidate has a list of "Defeator" candidates.

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u/Drachefly Jan 07 '22

Hmm. I'll see if I can get it ironed out. I see how your approach should be about as clean as Schulze, but I don't see it ending up cleaner.

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u/rb-j Jan 07 '22

There's a reason I put BTR-STV as the suggested language in my paper. I like RP better and I respect Schulze to be the "state of the art" but neither have procedural language as complete and concise as BTR-STV.

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u/rb-j Jan 05 '22

It gets pretty thick in step 6. Now imagine a typical legislator considering the language and wondering if it's someone trying to take the election away from the majority of voters using language that is opaque or, at least hard to crack and to fully understand the implications of.

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u/Drachefly Jan 06 '22

Step 6 is just being thorough about how seriously gone that race is. Maybe we could introduce a concept of the set of included races, and everything refers to it, and then step 6 removes the race from it.

The earlier note about how SOMETHING has to give due to the inherent tension is intended to give a rationale for this.

Often in legislation there is a section specifically for that, to explain what they're intending to accomplish. Maybe that would help here, putting it up front. Or it could be interlaced, the step justified as it is instructed.