[EM] Three rounds

[Raph Frank]

On Thu, Nov 13, 2008 at 2:39 PM, Kristofer Munsterhjelm
<km-elmet at broadpark.no> wrote:
> For honesty, then, we have to know which are the two best candidates. This
> sounds like a proportional representation problem with a "council" of two;
> however, such methods cannot be invulnerable to cloning, since the Droop
> proportionality criterion and clone independence contradict each other (by
> http://www.mcdougall.org.uk/VM/ISSUE3/P5.HTM , "clone-no-harm").

I disagree, a PR method is not what you want here.  If the best
candidate is cloned, then both clones should be picked as the top-2.

This will not happen with PR.  In the linear policy case, the best
candidate is at the 50% mark.  PR will likely elect candidates at the
33% and 67% marks.  Neither of those candidates is optimal.

In fact, I think that picking one of the 2 would be give roughly the
same result as the plurality system.

> Also, if we want to retain the properties of the first-round election
> system, and that election system is Condorcet, then one of the candidates in
> the runoff must be the CW (when it exists). I would go further and say that
> there's no need for a runoff if there's a CW, but others may disagree.

In a condorcet election, the top 2 candidates would be at the 50% mark
in the 1d policy space.

The runoff would held the voters decide from 2 pretty good candidates.

> The former
> destroys any chance of passing the DPC, since Droop proportionality is
> incompatible with Condorcet (by example given in the Voting Matters article
> linked to above).

I don't see why you want them picked by a PR method, the idea
shouldn't be to pick 2 candidates who each represent half of the
community, it should be to pick 2 that represent the whole community,

> Then where should you put the other candidate? Not to the right, because
> that would be biased against the left-leaning voters. Not to the left,
> because that would be biased against the right-leaning voters. So it must be
> another centrist, a clone. But what choice is that?

It is a choice.  First, there are more than 1 dimension in politics
and second, even if there wasn't it allows the voters pick the most
capable of the 2 candidates who both have similar policy views.

> Call the candidate that's retained from the first round to pass criteria,
> the retained candidate. Perhaps we could then say that if the retained
> candidate is off-center in n-space, then the right thing would be to pick
> the viable candidate closest to its antipode (reversed coordinates) as the
> other candidate. But what's a viable candidate?

You could deweight the votes that voted for the first winner.  This
would shift the winning point away from the centre.

>> 40: A1>A2>B>C
>> 08: A2>A1>B>C
>> 07: A2>B>A1>C
>> 25: B>A2>C>A1
>> 20: C>B>A2>A1
>> A2 would be eliminated first in IRV but here A1 and A2 form a party
>> (with 55 first preference votes) and therefore C will be eliminated
>> first, B next, and then A2 will win.
>
> This seems to be more of a problem with IRV, and so I'd say that a better
> solution would be to switch to another voting system rather than try to
> patch it up with party lists.

Also, the A2>B>A1 voters cannot be considered members of the A party.
This highlights a problem with the party list system, it assumes
voters are rock solid supporters of their first choice's party.