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

[Jonathan Lundell]

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"?