[EM] Burlington VT reconsidering IRV 10 years after IRV failed to elect the Condorcet Winner

[Kristofer Munsterhjelm]

On 03/12/2019 16.54, robert bristow-johnson wrote:
> 
> 
>> On December 3, 2019 4:03 AM Kristofer Munsterhjelm <km_elmet at t-online.de> wrote:
>>
>>  
>> On 03/12/2019 07.00, robert bristow-johnson wrote:
>>>
>>>  i got news from Burlington Vermont regarding ranked-choice voting (after all we went through a decade ago) and i might could use a little bit of help.
>>
>>
>> What are the news from Burlington?
>>
> 
> okay, Burlington is pretty liberal.  While there is one Republican in City Council (who also happens to preside over the council and even more coincidently was the Republican candidate for mayor in the 2009 IRV election, gathering the most 1st-choice votes but losing to the Prog candidate in IRV) the Progs in City Council have reintroduced a Charter Change resolution to return to IRV, now they are calling it "RCV" but it is the same Single Transferable Vote procedure used in RCV elections everywhere.  The language of the Charter Change is posted below.
> 
> But there was a little pushback from other councilors (and myself) for Burlington to not repeat mistakes from the past, namely that of electing a candidate other than the clearly shown Condorcet Winner.
> 
> This is all in a hurry.  In two weeks Council will make the decision whether or not to include the question to the ballot for Town Meeting Day in March 2020.  On Monday Dec 9th, the Charter Change Committee will consider the language of the bill and vote on what shall be brought to the whole Council to include on the ballot.
> 
> I want to figure out some good language to change this from regular-old IRV to Bottom-Two Runoff, Single Transferable Vote, BTR-STV .  If someone is good at writing legal language or if this BTR-STV has had legislative language written for it somewhere else, I would like to see it.
> 
> The language that needs to be changed, to make this RCV Condorcet-compliant is: 
> 
> "... The candidate with the fewest votes after each round shall be eliminated ..."
> 
> How can we clearly and concisely change that to Bottom-Two Runoff?

My first stab would be: "After each round, of the two candidates with
the fewest votes, the candidate ranked below the other by the most
voters shall be eliminated".

Alternatively "on the most ballots". Or "among the two candidates". Or
"of the two candidates with the fewest votes in that round".

Presumably there has to be some tie-breaking language for the case where
more than one candidate is last or next-to-last. But I suppose there is
some similar language for IRV as is.

If there is no equal-rank or truncation, you can also say "the candidate
ranked below the other by a majority of the voters".

The strategy to turn IRV into BTR-IRV is probably the best one. Woodall
is better than BTR-IRV, and you could turn the method into Woodall by
checking for a CW before a round starts, but then you'd have to define
what a CW means in a way that doesn't confuse people who are unfamiliar
with Condorcet.

Looking again at the language, point (3) is already rather convoluted.
Perhaps it would be better to split up the definition. Something like:

(3) If no candidate receives a majority of first preferences, an instant
runoff re-tabulation shall be performed by the presiding election
officer. The instant runoff re-tabulation shall be conducted in rounds.
In each round, each voter’s ballot shall count as a single vote for
whichever continuing candidate the voter has ranked highest, and
subsidiarily to determine what candidate to eliminate. After each round,
the two candidates with the fewest votes shall be considered for
elimination. Of these two candidates, the candidate ranked below the
other by the most voters shall be eliminated in that round. The counting
in rounds shall continue until only two candidates remain, with the
candidate then receiving the greatest number of votes being elected.

(Maybe also call it something else than "instant runoff re-tabulation"
because it's no longer IRV, but I can't think of a better name at the
moment.)

I'm much less certain about Woodall. See below for something I cooked up.

(1) The ballot shall give voters the option of ranking candidates in
order of 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, an instant
runoff re-tabulation shall be performed by the presiding election
officer. The instant runoff re-tabulation shall be conducted in rounds,
for which the counting shall be conducted according to the following
three points.
(4) If there exists a continuing candidate so that for every other
continuing candidate, the former candidate is ranked ahead of the latter
by a majority of the voters, the former candidate is elected.
(5) If there is no such candidate, each voter’s ballot shall count as a
single vote for whichever continuing candidate the voter has ranked
highest. The candidate with the fewest votes shall be eliminated, which
marks the end of the current round and the beginning of the next.
(6) The counting in rounds shall continue until a candidate is elected
or only one candidate remains, with the remaining candidate then being
elected.
(7) The city council may adopt additional regulations consistent with
this subsection to implement these standards.

(Strictly speaking, the latter half of point 6 is redundant because when
only two candidates remain, the winner beats the loser pairwise and
would be elected by point 4. But a potentially infinite loop looks more
dangerous than a finite one.)

I haven't written legislative language before, but maybe it can serve as
a starting point for others who have.

-km