If one really wants a two-party system and doesn't want voters to
change that fact then one could ban third parties and accept only two.
That would solve the spoiler problem :-). From this point of view e.g.
the US system is not really intended to be a two-party system but just
a system (target state unspecified) that has some problems with third
parties. On the other hand the option of third parties could be left
in the rules intentionally. The voters are given a chance to change
one of the two parties to some third party if they want that so much
that despite of the associated spoiler problems they will eventually
give the third party enough votes to beat one of the leading parties.
Actually two-party systems need not be based on two parties only
nation wide. In principle each district could have its own two parties
that are independent of what the two parties are in other districts.
There is however some tendency to end up with two or small number of
parties nation wide.
Juho
On Nov 3, 2009, at 9:22 AM, Kristofer Munsterhjelm wrote:
Juho wrote:
On Nov 2, 2009, at 4:50 PM, Jonathan Lundell wrote:
Is this acceptable PR? I hope your answer is "of course not" (if
it isn't, we can have that discussion).
I note that a two-party system can be seen as one style of
democracy that may be chosen intentionally. But if the target is to
have PR then such single-seat FPTP systems are of course not good
at all.
If the people truly want a two-party rule, then using STV (or some
other party neutral PR method) can't hurt - they'll have that two-
party rule if they want, and can at any moment escape from it if
they change their minds. See Malta.
In addition, if the method is any good "between the hard limits"
specified by the DPC or analogous proportionality criterion, then
there will be competition between the candidates inside of the
party. STV is IRV between the hard limits, so one may doubt how good
it is at this, but in reality, it does at least provide some measure
of that; my clustering methods are much more Condorcet and so
presumably would provide greater such competition. My
proportionality simulator shows it to be much better than STV, but
I've discovered that said simulator also has a significant small-
party bias, so I'm taking the results with some salt until I can get
proper correlation going.
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