[EM] "Unmanipulable Majority" strategy criterion

[Kristofer Munsterhjelm]

Chris Benham wrote:
> I have a suggestion for a new strategy criterion I might call 
> "Unmanipulable Majority".
>  
> *If (assuming there are more than two candidates) the ballot
> rules don't constrain voters to expressing fewer than three
> preference-levels, and A wins being voted above B on more
> than half the ballots, then it must not be possible to make B
> the winner by altering any of the ballots on which B is voted
> above A.*
> Does anyone else think that this is highly desirable?
>  
> Is it new?

I think it's new. I won't say anything about the desirability because I 
don't know what it implies; it could be too restrictive (like 
Consistency) for all I know.

It would be possible to extend this to a set. For instance: "if the 
method elects from a set w, then it must not be possible to make a 
candidate X outside w the winner by modifying ballots on which X is 
ranked above all in w".

Or a more general case, with constructive and destructive burial. 
Constructive burial would be trying to make Y win instead of X. 
Destructive burial would be trying to make X not win, though in that 
case you would have to consider what kind of ballots could be changed, 
since there's no equivalent of B in the destructive burial case. 
Destructive burial also sounds too strict, that no useful method could 
fulfill it (unless only very specific ballots were permitted to be 
changed, e.g those who rank X last).