[EM] Condorcet question - why not bullet vote

[robert bristow-johnson]

On Jun 16, 2010, at 1:30 PM, Peter Zbornik wrote:

> Dear all, dear Markus Schulze,
>
> I got a second question from one of our members (actually the same  
> guy which asked for the first time):
> If I just bullet vote in a Condorcet election, then I increase the  
> chances of my candidate being elected?

If there is a Condorcet Winner (CW), the answer is "no".  If there is  
no CW, then we have a "Condorcet paradox" or a "cycle" where Candidate  
Rock beats Candidate Scissors, Candidate Scissors beats Candidate  
Paper, and Candidate Paper beats Candidate Rock.  Then I won't say  
whether the answer is "no" for sure, but I am still convinced that  
cycles are rare and that a method like Schulze or Ranked Pairs  
resolves the cycles meaningfully.

> If I have a second or third option, the chances of my prefered  
> candidate to win is lowered?

Same answer as above.  If there is a CW, the answer is "no, it does  
not hurt your favorite.  It makes no difference to your favorite."

> Q: In this case why should any voter not bullet-vote?

The whole idea is to allow the voter expressivity in all election  
possibilities and to not burden the voter with the need to think or  
vote strategically.  If the voter thinks that Candidate A is a better  
choice than Candidate B (that is, if the election was a 2-person race  
between A and B, this voter would vote for A), then the voter ranks A  
above B and that's that.  Nothing more to worry about.  If the voter  
would vote for Candidate C over B in a 2-person race but not over A in  
a different 2-person race, then that voter would rank A highest, C  
next, followed by B last.  Bullet voting for A does not help A any  
more than ranking A highest and mutes this voter regarding a possible  
decision between B and C.

> I have some clue on how to answer, but not enough for an exhaustive  
> answer.
>
> My argument starts:
> If I vote for a candidate who has >50% of the votes, then it does  
> not matter if there is a second or third choice.
> If my prefered candidate A gets <50%  of the votes, then it makes  
> sense to support a second choice candidate B.
> However if the supporters of B only bullet vote, then maybe B's  
> supporters get an advantage over A?

No, not if either A or B (or C) end up as the Condorcet Winner.

> ... at this point I realize, that I don't know enough about  
> Condorcet and/or Schulze to answer the question.
>
> Why is it not rational to bullet vote in a Condorcet election if you  
> are allowed not to rank some candidates?

Because you lose your voice in a potentially decisive election between  
two candidates, neither whom are your favorite but one of them you hate.

> I guess you have discussed this question a zillion of times, so  
> please forgive my ignorance.

It's what it's all about.  According to my "Gospel of Fair Elections  
according to Condorcet", there are really no downsides if there is a  
clear Condorcet Winner (and I disagree with most of the rest of this  
mailing list about the "Dark Horse pathology").  And I believe that  
cycles (where there *is* no CW) are rare.  That's my religion.

--

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."