How do you compare a new entry all the ones that came before? Having a
policy for incomplete ballots isn't good enough because it doesn't compare
a new name to the other names on ballots before the first ballot to
include a new write-in candidate. So, there must always be a first pass
through all the ballots to collect all the names.
There is an out depending on the partial ballot policy. I'm trying to
write a ratings based implementation with signed ratings. Since voters can
express positive or negative I think it's fair to assign zero to unvoted
choices. This breaks summability because on encountering a new name you
can't go back and compare to ratings. If however an unrated choice is
assumed to be lower than all the rest, it's possible to record a new name
as having lost to every other choice on as many ballots as there have
been.
But I think the 'no-vote is negative-infitiy' policy pretty poorly
represents what voters want.
If anyone can poke a hole in this and suggest a one-pass summable
condorcet with write-ins algorithm I'd love to hear it.
Practically in the system I'm writing making it collect write-in names
before counting votes won't be a problem.
Also, I'll note that Approval is still summable with write-ins.
Brian Olson
http://bolson.org/
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