[EM] Spoilers

[Martin Harper]

Anthony Simmons wrote:

> This brought up a question for me.  Suppose a
> purely hypothetical Approval election in which
> there are two major parties, with candidates
> Mickey and Goofy.  A third party candidate,
> Roadrunner, is very popular, but is not expected
> to win.
>
> Roadrunner voters feel they should vote for
> Mickey in addition to their own bird, since if
> Roadrunner doesn't win, they absolutely don't
> want the election going to Goofy.  So most
> Roadrunner voters vote for Mickey too.
>
> On the other hand, Mickey voters think that if
> support for Goofy is so strong that he beats
> Mickey, then for sure he will beat Roadrunner
> too.  Thus, they figure that they shouldn't vote
> for Roadrunner, since that could build up support
> for Roadrunner to the point where, if Goofy
> doesn't win after all, the election could go to
> Roadrunner.
>
> The end result is that Mickey's perceived
> advantage over Roadrunner might get him elected
> even though Roadrunner might actually have more
> sincere approval than Mickey.

Just what exactly is "sincere approval" in this case? How do I measure
it? {genuine question: I don't want to guess from what you've written}

> Doesn't this sound a lot like the way Plurality
> and IRV suppress support for a third party by
> forcing voters to be insincere?

Approval does suppress support for an *apparent* third party. Plurality
and IRV do this too - but they both also suppress support for *genuine*
third parties as well. Approval won't do this. In addition Approval only
forces voters to be strategic, not insincere, which is "nicer" in some
way.