[EM] I need an example of Condorcet method being subjected to the spoiler effect if any

[Kathy Dopp]

Thanks Robert,

My question was strictly about Condorcet and I know already how to
generate IRV and spoiler cases, as I said.

Are you claiming that Condorcet methods are never subjected to a case
of a nonwinning candidate changing who would otherwise win?

This seems logical, given the method and what you say below. However,...

Do any others on this list agree though or if not, please provide an example?

Thanks.

Kathy

On Wed, Jan 20, 2010 at 7:34 PM, robert bristow-johnson
<rbj at audioimagination.com> wrote:
>
> On Jan 20, 2010, at 7:10 PM, Kathy Dopp wrote:
>
>> Is the Condorcet method susceptible to the phenomena of a
>> nonwinning candidate whose presence in the election changes who would
>> otherwise win the election, all else being equal?
>
>
> i changed the sentence form into a question.  i hope that was okay, Kathy.
>  don't wanna misquote anyone.
>
> i think that the answer is "no", if a Condorcet winner exists and that all
> bets are off if a CW does not exist, except, perhaps for these
> "strategy-resistant" methods such as Markus Schulze's method.  i sorta
> understand it, but since he hangs here, i think Markus should address the
> question if the Schulze method is spoiler free.
>
>
>> Could someone please provide me with an example of the spoiler effect
>> occuring with the Condorcet method  of counting rank choice ballots or tell
>> me why the spoiler effect doesn't happen with Condorcet in  a few words?
>
> in the ranked-order ballot, no matter what their absolute ranks are, if A is
> ranked above B (or A is ranked while B is not), that counts as a vote for A.
>  likewise for B ranked above A.  doesn't matter if they were ranked 4th and
> 5th.
>
> just like the IRV final round between A and B, Condorcet will total how many
> votes with A>B and compare that to votes where B>A.  whether C is in the
> race or not, for each individual ballot, if A>B with C on the ballot, A
> would continue to be ranked above B (whether C is higher than either, in
> between, or below either).  with the meaning of every ballot, regarding A
> and B, unchanged (whether C is there or not), the vote counts for A>B and
> B>A do not change.  so every Condorcet tally not involving candidate C will
> remain unchanged, the tallies involving C are not there if C is removed.
>
> if A (or whoever is not C) was the Condorcet winner before C was removed,
> then the A>X tally exceeds X>A for any X.   then A would continue to be
> ranked over all of the other remaining candidates with the same tallies as
> before even with C removed, because every tally not involving C would remain
> unchanged.
>
> i would say that (with the CW existing), it's spoiler-proof.
>
>>
>> Thanks. I'm devising an experiment to compare the Condorcet method
>> with the IRV method of counting rank choice ballots and would like, if
>> possible, to introduce subjects to the spoiler effect to see under
>> what conditions they notice it occurs.
>
> do you want me to tell you how it occurred in Burlington in 2009?
>
> --
>
> r b-j                  rbj at audioimagination.com
>
> "Imagination is more important than knowledge."
>
>
>
>
>



-- 

Kathy Dopp

Town of Colonie, NY 12304
phone 518-952-4030
cell 518-505-0220

http://utahcountvotes.org
http://electionmathematics.org
http://kathydopp.com/serendipity/

Realities Mar Instant Runoff Voting
http://electionmathematics.org/ucvAnalysis/US/RCV-IRV/InstantRunoffVotingFlaws.pdf

Voters Have Reason to Worry
http://utahcountvotes.org/UT/UtahCountVotes-ThadHall-Response.pdf

Checking election outcome accuracy --- Post-election audit sampling
http://electionmathematics.org/em-audits/US/PEAuditSamplingMethods.pdf