[EM] Why does IRV but not delayed top-two runoff lead to 2-partydomination?

[Michael Ossipoff]

Jan Kok wrote:

>The statistical evidence at http://rangevoting.org/TTRvIRVstats.html
>seems pretty good that IRV leads to two party domination in IRV
>elections, while (delayed) top two runoff tends to lead to a strong
>multiparty system.
>
>Why do those two methods, which seem strategically quite similar, lead
>to such different results?

In 2-balloting top-2 Runoff, the CW can't lose if s/he comes in 1st or 2nd 
in the first balloting.

You said:

>Most IRV supporters in the US have no clue that voting their favorite
>1st can ever hurt them. From my limited discussions with Australians,
>it seems most of them have no idea either.

I reply:

My discussions with Australians suggests the opposite. They told me that 
it's difficult for small parties to get 1st place votes, because voters 
don't want to waste their vote. Voters want to vote one of the big-2 
parties' candidates in 1st place, for strategic reasons. Do they know 
something about IRV that American IRVists don't know? :-)

One Australian I spoke with even told me that she herself had insincerely 
voted a top-2 candidate iln 1st place, insincerely downranking her favorite.

Mike Ossipoff