[EM] DH3 pathology

[Warren Smith]

>RL Suter:
To make a dire warning about how "DH3 pathology" could
cause "massive destruction" if any of the voting methods
that are theoretically susceptible to it are used is little more
than a rhetorical ploy...   What is most lacking in this and other discussions
on this list about strategic voting is empirical data about
how people vote in actual public elections in which different
voting methods are used...  If the point is to make
arguments that are logically compelling, such rhetoric
is not merely unhelpful but extremely counterproductive.

--REPLY by WDS:

The reason I consider DH3 to be extremely serious and destructive,
as opposed to some random election pathology example which is not
so serious, is that is is extremely COMMON and when it happens it is
very BAD.   It is the combination of the two

Why do I say COMMON?
   Because all you need are 3 major rivals and at least one additional
   "dark horse" candidate voters do not like and do not take seriously as
   a threat to win.    This is very common.   Indeed, pretty much the
   only occasions where this does not happen, are when you only have 2
   major rivials, in which case, since plurality is the best system in
   2-canddiate elections, the whole discussion about improving on plurality would
   largely be moot.   Assuming we are having such a discussion, then
   you have to regard DH3 as very common.

Why do I say BAD?
   Because it causes the candidate unanimously agreed worst, to get elected.
   That is as bad as it possibly can be.

I think these are objective criteria, not inflamed rhetoric. 
Warren D Smith
http://RangeVoting.org