[EM] SODA might be the method we've been looking for.

[Jameson Quinn]

I believe that LRV (Least Resentment Voting) is indeed quite a clever
solution to the chicken dilemma. But once more, I'd like to remind people
that there is a way to solve the chicken dilemma without risking a victory
by the plurality winner/condorcet loser. I'm speaking of course of SODA.

First, SODA meets the FBC. In fact, in any 3-candidate scenario, and I
believe in any 4-candidate one, it is strategically optimal to bullet vote
for a candidate if you agree with their declared preferences. This ability,
not just to vote your favorite equal-top, but unique-top, is not shared by
any other method I know of. (Perhaps we could call this UFBC3, unique FBC
for 3 candidates.)

How does it do with chicken dilemma scenarios? For the following, I'll give
honest ratings, then discuss the likely strategic implications under SODA.

40 C
25 A>B
35 B>A

If this is the honest situation, then candidates A and B have every reason
to find a way to include each other in their predeclared preference lists.
These predeclared lists are made openly, and so one side cannot betray the
other without giving the other side a chance to retaliate. The chance for
retaliation will make betrayal a losing strategy.

40 C
25 A
35 B>A

If the A camp is honestly indifferent between B and C, and candidate B
finds this indifference credible, then B can still decide not to retaliate,
that is, to ignore A's truncation and nonetheless declare a preference for
A. This enables A to win without B spoiling the election.

(Any single-round method which elects A here is subject to the chicken
dilemma; electing B is, in my mind, crazy; and any method which elects C
here has been spoiled by candidate B, and so encourages shenanigans of the
republicans-funding-greens sort. Any method I know of except SODA fails in
one of these ways.)

40 C
25 A>B
35 B

This is like the above situation, but since A had no chance of winning
anyway, they have even less of a motivation to retaliate against B, whether
or not B's truncation is honest.

40 C>>A
25 A>>B
35 B>>A

In this situation, it's difficult to say who's the "correct" winner;
depending on the underlying utilities, it could easily be any of the three,
so I'd have no problem with a method that elected any. Still, ideally a
method would give similar results here as in the situations above, so that
candidates and voters are not motivated to be conciliatory, rather than
projecting an image of someone who's inclined to truncate.

Strategically, it is in B's interest to truncate, to reduce the chance of
10 C>>A voters voting CA and thus giving A the all-important second move in
the vote delegation stage. Then, candidate A will declare a preference for
B, in order to present C with a credible threat. And candidate C will
declare a preference for A to prevent B from winning.

40 C>>A???
25 A>B
35 B>>A???

This is the "weak condorcet winner" situation. The question marks denote a
"preference" for the dark-horse candidate A which would evaporate in a
runoff, when people took a hard look at A without being distracted by the
C/B rivalry. If that is the case, A should not win. And indeed, even if C
predeclares a preference for A, when C is faced with the morning-after
reality of the choice to throw the election to A or allow it to go to B,
they have a chance to leave it with B if A is really such a bad candidate.
Sure, C may prefer a weak winner who owes them a favor to a stronger
opponent, and so elect A even if B would be socially-optimal; but at least
SODA gives B a chance in this situation. Any Condorcet method would simply
elect A and not look back.

I think that the situations above show that SODA always allows honest
truncation without a strategic penalty, but does not encourage strategic
truncation.

I know that some people on this list dislike SODA for its delegation.
Obviously, I disagree. Consider:
- SODA delegation is optional and eyes-open. Because of pre-declaration,
you know what kinds of result your delegated vote could and could not
promote, and if you don't like those results, you don't delegate.
- SODA delegation allows results that seem to me to be obviously better
than other methods in the above scenarios.
- SODA delegation allows for unmatched simplicity from the average voter's
perspective. If you like your favorite's declared preferences, just vote
for them, and you're done.
- SODA delegation allows significant minority candidates a moment of
personal power, which they can use to extract (non-binding) promises before
throwing their votes behind someone. I believe that this transitory moment
of minority power is a healthy compromise between the stability and
leadership in winner-take-all systems and the broader accommodation of
minority interests in parliamentary systems.

Of course, there are cases where SODA is not ideal. For instance, for a
pre-election poll, SODA cannot be used unless the inter-candidate
preferences can be somehow known or inferred. Still, I think SODA is
overall a standout good method for most cases where high-stakes
single-winner elections are appropriate.

Jameson
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