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Warren,<br>
You and Jobst recently had this exchange about Definite Majority
Choice (DMC) and Range voting. You begin by quoting<br>
one of Jobst's "15 reasons to support DMC".<br>
<br>
<blockquote type="cite">
<pre wrap="">6. Robustness against "noise" candidates.. cloneproof...
</pre>
<pre wrap=""><span class="moz-txt-citetags">WS: > </span>--also true of range.
</pre>
<pre wrap=""><!---->
JH: Could you say more precisely what you mean here?
WS:--Range voting is immune to clones in the sense that any number of cloned
candidates, all of whom get the same rangevote scores, can be added to the scene,
and the election winner will remain unchanged (except perhaps for replacement by a clone).
Also, if "noise" candidates are added who have no hope of winning, then the range votes
with noise scores being adjoined for the new candidates, will still yield the same winner
and indeed the same totals.
Many other voting schemes have these properties (and many also do not
have these properties) but in range's case it is particularly self-evident.</pre>
</blockquote>
Range only has this property in a technical sense, in a way that is
connected with its technical failure of May's axiom, i.e. it<br>
doesn't reduce to FPP when there are only two candidates. <br>
<br>
Suppose that in the period leading up to the election it is known for
sure that two candidates will stand, A and B. A is a left-wing<br>
candidate that is hated by big money and its mass media. B is a
centre-right candidate that they like. Reliable but perhaps not widely<br>
published polls give A52%, B48%. The method to be used in the
election is Range, and with just these two candidates standing<br>
the voters have no reason not to give maximum points to their preferred
candidate and minimum to the other resulting in a solid win<br>
for A. <br>
How to change B from being the majority loser to the "super-majority
consensus candidate"? Easy! A third candidate, C is nominated.<br>
C is a horror far-right candidate. Maybe some of A's supporters are
members of some ethnic/racial/religious minority that the C<br>
candidate says he's in favour of persecuting. Anyway, now all the mass
media have to do now is to convince some of A's supporters<br>
that C has some chance of winning the election, or just that they
should give a maximised sincere vote.<br>
<br>
So without C we have:<br>
52: A99, B0<br>
48: B99, A0<br>
A wins 5148 to B4752.<br>
<br>
With C added and some of A's supporters conned and/or frightened,
this could become:<br>
47: A99, B0, C0<br>
05: A99, B98, C0<br>
46: B99, A0, C0<br>
02: C99, B98, C0<br>
<br>
Now B wins: B5242, A5148, C198. (Approval is also vulnerable to
this scenario.)<br>
Note that in this example the voted and sincere (binary) pairwise
preferences are A>B 52-48, A>C 52-2, B>C 98-2.<br>
<br>
I think DMC is a very very good (possibly the best) single-winner
method to propose for public office elections if we insist on
Condorcet <br>
and Mono-raise.<br>
<br>
<br>
Chris Benham<br>
<br>
.<br>
<br>
<br>
<br>
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