[EM] unsatisfied with implications of Condorcet method (fwd)

[Rob Lanphier]

Hi everyone,

I received the following private message about burying preferences in a
Condorcet election.  I'll also send my response so that you can see what
I've already said, but I'd also like to understand if the various
improvements to Condorcet (e.g. Condorcet-SSD) have any effect on this.

I was asked to strip out the identifying characteristics.  Suffice it to
say, this person has lots of real world experience with Instant Runoff
Voting (IRV).  He refers to it as "STV" (Single Transferrable Vote).

Rob
---------- Forwarded message ----------
Rob,

I was interested in your interactive demo of Condorcet's method, and I
decided to try it out with some real world numbers.  I am a member of the
xxxxxxxxxxxxxxxxxxxxxxx, a notoriously factionally divided organisation.
One recent election for a single position saw three candidates - a
moderate left-winger, a fairly "harmless" centre candidate, and a more
extreme right-winger.  The left-wing candidate had the support of a
binding faction (the Left - my faction), which means that we all decide to
vote in a way which will best further our political aims - to pull party
policy towards socialism.

Because the right wing candidate was an extremist and had marginalised
himself, he only had the votes of a small number (5) of hard-core
supporters.  These all preferred the centre candidate to the left.

The centre voters (16) all preferred the left to the right, as our
candidate was more moderate.

The election was conducted under preferential, STV style voting.  We (the
Left) therefore decided to preference second to the Centre candidate, to
ensure that the Right candidate didn't win.  This meant that the right
wing candidate was eliminated first, and all his votes transferred to the
Centre candidate, who won.

If this election had been conducted under the Condorcet method, I believe
we could have "rigged" the election so the Left candidate won instead!
Here's how I represented this election in your demo:

1,Joan Left
2,Sam Middle
3,Max Right
19:1>2>3
16:2>1>3
5:3>2>1

On these figures, the Centre candidate should clearly win.  He wins every
pairwise contest.

But if we in the Left decided to preference instead to our right-wing
enemy, it goes like this:
19:1>3>2
16:2>1>3
5:3>2>1

This results in a Condorcet tie-breaker, which is won by Joan Left, given
that she had the most primary votes.  This means that in order to ensure
victory, we should vote "against our principles", for the right wing
extremist!

This works for a fairly wide range of numbers - anywhere between 17 and 21
Left voters would make the same decision against 16 Centre and 5 Right.

And if you don't believe we're that cunning to work out the numbers like
this beforehand, think again.  We stage manage elections as best we can,
because the other side are doing the same thing. :)

I'm interested to hear your defense of the Condorcet method in this case,
given that it encourages people to vote en-bloc against their true
preferences, in order to ensure victory for their favourite candidate.

(end of message)

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