[EM] Condorcet Meeting: Narrowing the Field

Colin Champion colin.champion at routemaster.app
Fri Sep 1 08:47:18 PDT 2023

It seems to me that the position is this. Condorcet voting works well 
under certain assumptions, which include voters sincerely ranking all 
candidates in order of preference. Strategic voting turns out to be less 
of a problem than one might fear, but drastic truncation is fatal.
    The merits of Condorcet voting lie partly in its not penalising 
minor parties, so you'd expect it to lead to an explosion in the number 
of candidates.
    So you're organising a presidential election, hoping to take 
advantage of the merits of Condorcet voting, and you expect 500 
candidates to put themselves forward. What do you do?
    One no-brain solution is to run a Condorcet election with 500 
candidates. Another is to rely on administrative procedures, eg. only 
the 5 candidates with most supporting signatures get onto the ballot. 
This isn't a bad idea; something like it is widely practised. I think 
the Virginia meeting is intentionally allowing it as an option. Can we 
do better?

There are no particular constraints or objectives on a first round - 
what matters is how well the system as a whole performs.
    It may be that Forest is trying to get only centrist candidates 
through to the second round. I think this is a bad idea. The second 
round cannot elect a bad candidate in his scheme, but non-centrist 
voters are likely to feel they have nothing to play for and stay at 
home. The result of the second round will therefore be skewed and 
    The problem lies in the questionable performance of ranked voting 
with large fields. It seems to me that both Chris and Forest are trying 
so hard to get the optimum set of survivors to the second round that 
instead of solving the problem they end up shifting it to the first round.

On 01/09/2023 00:39, C.Benham wrote:
> Forest,
> I gather you envisage a high-turnout primary election with the final 
> being held as soon as practicable afterwards.
> On the issue of whether or not we sometimes dispense with the final 
> because one candidate was so dominant in the primary,
> we could have a rule about the winners final-two IRV count (or maybe 
> some alternative, like minimum pairwise support) as a proportion
> of the total number of eligible voters.
> If that is too low, then maybe we can have a final anyway, say between 
> the IRV winner and the candidate  with the most pairwise opposition
> to the IRV winner  (and maybe if that isn't the IRV last-2 runner-up 
> that candidate also if that pairwise result was "sufficiently", 
> according to
> some rule we make up, close).
> There should be no simple rule that says we always have a final if the 
> turnout for the primary is below X%, because that could sometimes cause
> some faction of voters to have a strategic incentive to abstain from 
> the primary.
> Chris B.
> On 1/09/2023 6:37 am, Forest Simmons wrote:
>> Say the finalists are the IRV winner together with any and all of its 
>> "enemies" (defined as those candidates that defeat it pairwise).
>> If the IRV winner has no enemies, no need for any further runoff 
>> beyond the Instant Runoff that just popped out the IRV winner.
>> If the IRV winner has precisely one enemy, then the two-candidate 
>> final runoff will be a no stress sincere choice for the voters.
>> Otherwise, you have a potentially interesting runoff with "around 3 
>> to 5 candidates" to put the Condorcet Meetng through its paces.
>> fws
>> On Thu, Aug 31, 2023, 11:51 AM Forest Simmons 
>> <forest.simmons21 at gmail.com> wrote:
>>     Could the Implicit Approval winner ever be a Condorcet loser?
>>     Highly unlikely, especially in the context of too many
>>     candidates, etc. But if so, every other candidate would have a
>>     short beatpath to it ... so no narrowing of the field would occur.
>>     So it would be better to use the IRV winner or the MaxMax
>>     Pairwise Support winner as the short beatpath target ... the
>>     winner of the simplest method that satisfies the Condorcet Loser
>>     Criterion.
>>     On Wed, Aug 30, 2023, 11:30 PM Forest Simmons
>>     <forest.simmons21 at gmail.com> wrote:
>>         Voters strictly rank as many candidates as they care to.
>>         The implicit it approval of a candidate is the number of
>>         ballots on which it out ranks at least one other candidate.
>>         Let S be the set of candidates tied for most implicit approval.
>>         A candidate will advance to the final ballot if and only if
>>         it has a beatpath of two or fewer steps to some member of S.
>>         fws
> ----
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