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

[Terry Bouricius]

Jonathan makes an important point. The term "spoiler"  means a minor 
candidate with a small percentage of the vote, who changes which of the 
other candidates wins by running. But Kathy and some others wish to expand 
the definition to include a front-runner. (Note that these IRV opponents 
refer to the top plurality vote-getter who narrowly lost the runoff in 
Burlington, Kurt Wright, as a "spoiler" who prevented the candidate in 
third place from winning. This is a dynamic worthy of analysis, but the 
word "spoiler" is never used by the media or political scientists when 
describing the plurality leader.

Terry Bouricius

----- Original Message ----- 
From: "Jonathan Lundell" <jlundell at pobox.com>
To: "Juho" <juho4880 at yahoo.co.uk>
Cc: "EM Methods" <election-methods at lists.electorama.com>
Sent: Thursday, January 21, 2010 10:33 AM
Subject: Re: [EM] I need an example of Condorcet method being subjected 
tothe spoiler effect if any


On Jan 21, 2010, at 1:03 AM, Juho wrote:

> What is good in all the common Condorcet methods is that their 
> vulnerabilities to strategies (and their differences in general) may 
> very well be so small in typical real elections (large, public, with 
> independent voter decision making, with changing opinions and less than 
> perfect poll information) that strategic voting will not be a problem. 
> Also their differences with sincere votes (e.g. spoiler related 
> problems) are quite small in real life elections.
>
> Here's one simple spoiler related example as a response to Kathy Dopp's 
> request.
>
> 35: A>B>C
> 33: B>C>A
> 32: C>A>B
>
> I this example there are three candidates in a top level cycle. If any 
> of the candidates would not run that would mean that there is a 
> Condorcet winner, and that winner would be different in each case. Let's 
> say that the method we use will pick A as the winner. If B would not run 
> then the votes would be 35: A>C, 33: C>A, 32: C>A and C would win. B is 
> thus a spoiler from C's point of view.
>
> I note however that these spoiler cases in Condorcet are not as common 
> as in many of the other methods. In practice it may be that there is no 
> need to worry about these cases. Maybe Kathy Dopp's comparisons will 
> reveal something about how problematic the spoiler effect is or is not 
> in Condorcet. Not also that in the example above B was not a minor party 
> candidate (often term spoiler refers to minor candidates) but a pretty 
> strong candidate.

In that case it might be a good starting point to define "spoiler", so we 
know what we've found when we find it.

What's an example of an IRV spoiler who's not a "pretty strong candidate"?
----
Election-Methods mailing list - see http://electorama.com/em for list info