[Election-Methods] Is this Condorcet method reasonable?
SEppley at alumni.caltech.edu
Wed Dec 12 08:10:11 PST 2007
Juho Laatu wrote:
> On Dec 11, 2007, at 0:02 , Steve Eppley wrote:
>> If candidates may not withdraw after the voting, some of them may be
>> forced to withdraw before the voting (also known as "deciding not to
>> run, out of fear of being a spoiler that worsens the outcome") or some
>> voters may be induced to vote insincerely.
> Fortunately the results of the election are typically not known
> beforehand. Therefore the reasons and information behind a withdrawal
> before the election are typically quite different from what they would
> be after the election.
As I wrote in my previous email (above) what I meant by "withdrawing
before the election" is deciding not to run. Even without precise
knowledge, fear of spoiling will motivate candidates not to run. In
partisan elections, the decision not to run will typically be made not
by the individual but by his/her party. If the voting method is
spoiler-prone, the party will be afraid to nominate a potential
spoiler. Even in non-partisan elections, fear of being a spoiler (given
a spoiler-prone voting method) will deter potential candidates from running.
> I also note that e.g. in the US presidential elections there have been
> few spoilers and many candidates that could have become spoilers but I
> think there are not many that would have given up the race already
> before the election.
That is not what I have observed. Ask yourself why do the parties each
nominate only one person per office? The reason is to avoid spoiling
and losing. Many people have competed to be the nominee of one of the
two big parties, and nearly all who failed to be nominated chose not to
compete in the general election.
>> I've observed considerable
>> voter negativity regarding not having a good enough candidate to vote
>> for on election day, in systems where spoiling prevents candidates from
>> running, and having to "hold one's nose" while casting a vote for a
>> less-preferred candidate. I expect there would be considerable voter
>> negativity regarding the need to vote strategically in systems that do
>> not permit withdrawal.
> After an election with withdrawals there can be two winners - one that
> would have won based on the ballots and one that won as a result of
> the withdrawals. Maybe the voters that supported the first "winner"
> are also disappointed with the method. That may be true especially if
> the first winner did not "win" as a result of strategic voting. Or if
> most of his supporters think so.
Yes, but all voting methods are subject to disappointment by supporters
of a loser, particularly if there exists another voting method that
would have elected their preferred candidate. So, why single out
withdrawal methods for this criticism? Furthermore, why believe that
disappointment with a withdrawal method will be greater than
disappointment with methods where voters must calculate and organize
strategies every time there's a high-stakes election?
It appears to me that critics of withdrawal are forgetting that the
incentive for candidates trying to win will be to compete to be the best
compromise. Their positions on the issues will be similar. Assuming
this is so, and assuming the underlying voting method chooses from the
top cycle, how great could the voters' disappointment be? Here's a
spatial diagram to illustrate my point:
L C1 R
Assume C1, C2 and C3 cycle. Since they are spatially near each other,
the disappointment of the voters who prefer the pre-withdrawal winner
should not be intense.
Assuming the C candidates are similar on the issues, I would NOT expect
the voters' ranking of the C candidates in such elections to resemble
the classic example of majority cycling:
?% ?% ?%
C1 C2 C3
C2 C3 C1
C3 C1 C2
I would expect the voters to be far more split: a significant number of
voters who rank C1 first would rank C2 second and a significant number
of voters who rank C1 first would rank C3 second, etc. I would also
expect the voters' preference intensities regarding the C candidates to
be relatively small compared to the intensities involving L and/or R. I
would expect the candidates' and parties' preference intensities
regarding the C candidates to be small too.
Assume C1 > C2 > C3 > C1 (where '>' means "is ranked by a majority
over") and that C1 wins if no one withdraws. It has been suggested that
C3 may pay C2 to withdraw. If so, why care? Elections are crude
instruments for making social choices. Furthermore, C1 has the moral
high ground and could offer to pay C2 not to withdraw or could offer to
pay C3 to not pay C2.
Note the similarity between withdrawal and parliamentary coalition
formation. When parties form a coalition to select the executive
cabinet officers (in particular, the prime minister) they are not bound
by the votes of the recent election. Who knows what deals they will
make? At least with withdrawal, all a candidate can do is step out of
the way of their supporters' next choice.
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