[Election-Methods] USING Condorcet

[Kevin Venzke]

Hi Juho,

--- En date de : Jeu 3.7.08, Juho <juho4880 at yahoo.co.uk> a écrit :
> That scenario was the simplest I could imagine. Only three 
> candidates. One strong candidate but below majority, one
> weaker  
> runner-up, and third clearly weaker candidate. This was
> also the most  
> threatening scenario from burial point of view that I could
> imagine.  
> Are there simpler and more threatening ones?

Again, it isn't enough to isolate the scenario where the strategy
succeeds. What matters is the scenario where the strategy is worth
attempting. It is no consolation that the strategy does nothing when
the strategizers' candidate is the CW (due to a majority or due to
second preferences from the third candidate's supporters), or when creating a cycle doesn't change the winner.

The strategy has to hurt their own interests. Call the major candidates
A and B, with the third candidate being C. A voters will use burial
strategy. Why would they not?
1. Because it could move the win from A to B: Impossible because this
would violate monotonicity.
2. Because it could elect C: Only when the B voters use burial strategy
themselves. (We're assuming everyone will give full rankings of course.)

Even though the strategy may hardly ever *work*, it's quite unlikely that
it will hurt to try it, unless the opposing voters are using it too.

Compare with an IRV voter who uses burial because it feels right and isn't
expected to make any difference. I don't think you have to be a thief,
or even trying to deter thieves, to use this strategy. 

By the way:
C is a minor candidate who makes it onto the ballot without anybody 
knowing much about him except his few supporters. I guess you don't have 
candidates like C in your country, since you always seem to speculate
about how many second preferences he would be getting in a real election.
Maybe Condorcet would encourage a better candidate than C to enter the
race (call him "D") but it's not clear that Condorcet would make C go
away or that there always would be a D candidate.

Even if A and B voters "sincerely" give C a second preference, essentially
ranking the unknown option above the competition, I consider it hardly
any different from using burial strategy, in terms of its destructive
effect on the outcome.

Kevin Venzke


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