[EM] Condorcet strategy and anti-strategy measures

[Markus Schulze]

Dear James Green-Armytage,

you wrote (26 May 2004):
> I think that 2 balloting wv Condorcet (2nd balloting only in
> the event of a cycle, and with the option for candidates to
> withdraw *in between* ballotings) is an extremely good proposal
> for public elections. This is what I would propose for a public
> election if anyone seriously asked me now.

I don't think that having a second balloting is a good idea.

1) When you promote a second balloting then you make the readers
   mistakenly believe that Condorcet methods have a serious
   problem when there is no Condorcet winner. However, in my
   opinion, the currently discussed Condorcet methods (esp.
   Tideman's ranked pairs method, Heitzig's river method,
   my beatpath method) are very good single-winner election
   methods even in the absence of a Condorcet winner, since
   these methods also satisfy monotonicity, reversal symmetry,
   independence of clones, majority for solid coalitions, etc..
2) A very important argument for preferential ballots is that
   they don't require a second balloting. When you promote
   a second balloting even for preferential ballots then you
   lose one of your arguments for preferential ballots.
3) The probability is very large that in the second balloting
   there are only candidates of the same party. Voters who
   don't support this party will then be deterred from
   participating at the second balloting.
4) A second balloting will encourage the voters to vote
   insincerely in the first balloting. The voters will believe
   that they can vote insincerely in the first balloting
   without any risk; these voters will believe that they can
   see in the first balloting whether their strategy would
   strike back so that (when they see that it would strike back)
   they can still vote sincerely in the second balloting so that
   they don't risk anything when they vote insincerely in the
   first balloting. A second balloting will also encourage the
   voters to vote insincerely in the second balloting because
   they will believe that they have very precise information
   about the strengths of the candidates.

Markus Schulze