[Election-Methods] A better IRV (was Re: Range Voting won't eliminate spoilers)

[Chris Benham]

Steve Eppley wrote:
"IRV might cause polarization even worse than what we already have, since 
the effective plurality rule campaign strategy of shifting toward the 
centrist swing voters after being nominated--which reduces polarization 
somewhat--would risk, under IRV, the late entry of an independent 
candidate competing at a position slightly closer to the party base."

Some people might think that (for many elections) providing voters with extra
meaningful choices is more important than  "reducing polarisation".


"IRV can be significantly improved by letting candidates withdraw from 
contention after the votes are cast."

That is debatable. This seems to be based on the assumption that IRV is a
lousy method because it fails Condorcet and Minimal Defense and when on 
the sincere preferences there is a Condorcet winner who is not a Dominant
Mutual Third (DMT) winner then some of the voters have incentive to use the 
Compromise strategy; and so that any modification that reduces these 
problems must be a big unambiguous improvement.

On the other hand I consider that it is one of the good methods because it has
some redeeming positive properties that are incompatible with those that it lacks.

One of its good properties (criterion compliances) that endears it to its supporters
is that it meets Later-no-Harm.  IRV "improved" in the way Steve suggests doesn't.

49: A
24: B (sincere is B>C)
27: C>B

Normal IRV elects A. The voters have no incentive to truncate, including the 24 B
voters who could have created a preferable result for themselves (the election of C)
by voting their full sincere rankings.

But with Steve's suggested option of allowing candidates to withdraw after the ballots
have been cast and analysed, the B supporters' truncation can pay off  if  C plays the
game and withdraws. If they don't insincerely truncate then B can't win (unless C is 
somehow induced to withdraw from an unassailable win), so that is a failure of  
Later-no-Harm.

As I made clear in a previous post, I am philosophically opposed to to having the results 
of elections determined by the machinations and manoeuvres of  candidates/parties 
*after* the voters have cast their ballots.

Chris Benham



Steve Eppley wrote Mon Mar 17  2008:

...However, IRV is worse at eliminating spoilers than some other methods.  
It also undermines candidates who take centrist compromise positions, by 
defeating them and making them appear unpopular.  As a consequence, we 
can expect IRV would continue the "two big polarized parties, each 
nominating one candidate per office" system (including its haphazard 
primary elections).

IRV might cause polarization even worse than what we already have, since 
the effective plurality rule campaign strategy of shifting toward the 
centrist swing voters after being nominated--which reduces polarization 
somewhat--would risk, under IRV, the late entry of an independent 
candidate competing at a position slightly closer to the party base.

IRV can be significantly improved by letting candidates withdraw from 
contention after the votes are cast.  At the end of election day, the 
votes would be published in a format that candidates (and others) can 
download.  Then the candidates would be given a few days to decide 
whether to withdraw.  They could use those days to calculate what the 
result would be with or without themselves (and/or some other 
candidates) in the voters' rankings, and to negotiate with supporters 
and with other candidates about who, if anyone, should withdraw.  The 
official winner would not be tallied until after the withdrawal period.

--Steve


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