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

[Juho]

On Jan 22, 2010, at 12:05 AM, Kristofer Munsterhjelm wrote:

> Jonathan Lundell wrote:
>> 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"?
>
> A very abstract concept of spoiler might be: denote f(X) the minimal  
> number of ballot changes/additions required to make X the winner.  
> Then a spoiler is a candidate with a high f-value relative to the  
> number of ballots (thus "hard to get to win"), who, by his presence,  
> still changes who wins.
>
> Determining f(x) for the various candidates would be very hard,  
> though, and one also runs into the question of what threshold to say  
> "above this f-value, spoiler, below it, not a spoiler".

Maybe one should add also the requirement that the spoiler makes the  
result worse from spoiler's or spoiler's supporters' point of view.

Another possible modification is not to require f(X) to be high. One  
would just see what would have happened with and without the spoiler.  
According to that definition also strong candidates (but not actual  
winners) could be spoilers. (Typically term spoiler refers to minor  
candidates since these discussions typically refer to a two-party set- 
up, but the corresponding scientific term might or might not be  
limited to minor candidates and/or this particular set-up.)

Juho