[EM] Strategy thoughts

[Dave Ketchum]

On Dec 5, 2009, at 7:41 PM, Dave Ketchum wrote  on:  Election Goals &  
Methods - a review:

Here I explore some possibilities based on using margins.  Assuming  
polling has given perfect knowledge as to the voting without strategy,  
what change might a strategist propose for the one group of voters  
that hears strategy gimmicks.
>
> 100 votes:
> 45A
      5A,B - these 5 voters add in B as second choice.  Effect is  31B  
to 29 C and B winning.
> 11B
      3B,A - effect is 48A to 44C and B winning (3 vote margin is less  
than this 4 vote margin).
> 15B,C
      3B - effect is 45A to 41C and B winning.
> 29C,B
      6C,A - effect is 51A to 49B and A winning (hard to sell, since C  
wins without strategy).
>
> The pairwise defeats are as follows:
> B beats A, 55 to 45 (55 winning votes, a margin of 10 votes)
> A beats C, 45 to 44 (45 winning votes, a margin of 1 vote)
> C beats B, 29 to 26 (29 winning votes, a margin of 3 votes)
>
> Using the winning votes definition of defeat strength, the defeat of  
> B by C is the weakest, and the defeat of A by B is the strongest.  
> Using the margins definition of defeat strength, the defeat of C by  
> A is the weakest, and the defeat of A by B is the strongest.
> Using winning votes as the definition of defeat strength, candidate  
> B would win under minimax, Ranked Pairs and the Schulze method, but,  
> using margins as the definition of defeat strength, candidate C  
> would win in the same methods.
> If all voters give complete rankings of the candidates, then winning  
> votes and margins will always produce the same result. The  
> difference between them can only come into play when some voters  
> declare equal preferences amongst candidates, as occurs implicitly  
> if they do not rank all candidates, as in the example above.
>
> Dave Ketchum
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