[EM] SFC and "margins vs. winning votes"

[Daniel Bishop]

Kevin Venzke wrote:

>>As Blake pointed out, we can think of truncated votes as more or less 
>>equivalent to the same votes completed with random rankings. In that 
>>case, any margin of victory translates to a majority victory.
>>    
>>
>
>So, what do you make of my favorite scenario?:
>
>49 A
>24 B
>27 C>B
>
Consider the ballots:

49 A
24 B
24 C>B

Then A (who beats B 49-48 and beats C 49-24) is the Condorcet winner.  
Note that this result was obtained by removing 3 ballots from the 
original set, and that there is no way to elect A by removing fewer 
ballots.  Therefore, declaring A the winner is the equivalent of 
ignoring the wishes of 3 voters.  Similarly, by eliminating 7 ballots (3 
A's and 4 C>B's), then B (who beats A 47-46 and beats C 24-23) becomes 
the Condorcet winner.  Or by eliminating 23 ballots (all of them A's), 
then C (who beats A 27-26 and beats B 27-24), becomes the Condorcet 
winner.  In summary,

* Electing A is equivalent to discarding 3 ballots
* Electing B is equivalent to discarding 7 ballots
* Electing C is equivalent to discarding 23 ballots

Based on this argument, A should be elected.

I know you're asking, "What if the sincere preferences were 49 A>B>C + 
24 B>C>A + 27 C>B>A?  Then B would be the sincere Condorcet winner."  
But if this were the case, then the B>C>A voters would have been better 
off voting sincerely.  So why didn't they?