Mike’s talking outcomes, John’s talking mechanics. Of course with a single position to be filled, some of the best features of STV - distribution of surpluses and fractional votes – don’t come into play. But yes, IRV is just an instance of STV with the quota being 50.01% The voter still has a single vote that can be transfered among candidates in a downward order of preference.

As John says, let’s agree to disagree.

Some people regard STV as applying only to multi-member electorates and others don’t. Let’s agree to differ on this one.

No, it’s not. Completely unnecessary, in fact.

It is extremely important that Adolf Hitler is eliminated first off

No, it’s not. All you need to care about is that Hitler’s not elected.

and therefore has no real influence on the outcome.

All voters should have an equal impact on the outcome. So if a minority of voters prefer Hitler, it’s important where their second and subsequent preferences lie.

George Washington or someone very popular is bound to win in any system.

Yes. A popular candidate can win straight away with more than 50% of the first preferences.

You need to eliminate the really ones right off.

Not sure what this means. Perhaps an example is best.

Hitler is prefered by 32% of the electorate. The remaining 68% of voters split their preferences among the other four candidates: Angela, Berthold, Dietrich and Eberhard. As long as the anti-Hitler voters give Adolph their 5th (least) preference he cannot win.

This will be true even if A, B, C and D poll 19%, 18%, 16% and 15% respectively of the votes – a split that would give Hitler the victory in a first-past-the-post election.

[In this scenario neither Dietrich or Hilter can win – Dietrich will be eliminated first and his preferences distributed among A, B and C. Which of A, B or C is ultimately elected will depend on the flow of preferences – mathematically one of these three must be eliminated before Hitler is inevitably eliminated.]

It doesn’t. Those who give their first preferences to the least popular candidate never see their candidate win.

Those who give their first preferences to the second least popular candidate can sometimes see their candidate win.

The winning candidate is always the candidate who wins the two party preferred vote. That is, the candidate who is preferred by a majority of voters to the next most popular candidate.

Huey, Dewey, Louie, and Fred are all running for dogcatcher. Huey gets 43%; Dewey gets 11%; Louie gets 30%; and Fred gets 16%.

Since Dewey came in last, the first thing that happens here is that his votes get redistributed, according to their second-place choice, between Huey, Louie, and Fred. If enough of Dewey’s voters chose Huey in second place, Huey gets past 50% and wins.

Which means that more than 50% of voters prefer Huey over Louie.

If not, a further runoff ensues and it’s not inevitable that Huey will ultimately win.

In this particular example only Huey and Louie have a chance of winning. Even if all Dewey’s preferences flow to Fred, Fred still only has 27% of the vote and will be cut-up before Louie.

It can be surprisingly difficult to make a strong case for why, at the start of the automatic-runoff process, Dewey’s voters should have so much more “kingmaker” power than (for instance) Fred’s.

They don’t. If Dewey’s preferences all flow to Louie and Fred’s preferences all flow to Huey then it’s Fred’s preferences that have elected Huey with 59% of the two party preferred vote. In this scenario that’s a great outcome – Huey is preferred over Louie 59% to 41%

It’s been pointed out that the voter experience of IRV and Condorcet is the same—only the counting is different. So once IRV is in place, moving to Condorcet would be relatively easy, technically at least.

In SF, due to voting equipment limitations, the voter can rank only three candidates, something of a shortcoming in SF’s big fields of candidates. That restriction will no doubt be lifted in the relatively near future as SF updates its equipment.

IRV was something of an easier sell in SF because there was already a runoff system in place—the mayor, for example, must get 50%, or there was a runoff election between the top two vote-getters. These runoffs happened pretty much every election; they were expensive; and they had very low turnouts, as a rule.

So IRV (SF calls it “ranked-choice voting”) was an easier sell, as an improvement to the existing not-so-instant runoff scheme.

Query for the group: Would the proposed voting reforms have flipped the outcome of the 1992 US presidential election, resulting in the reelection of Bush 41?

How would the Democratic Party nomination in 2004 have come out if there was one national IRV vote among praimary voters in all 50 states? Would Dean, reinforced with Kucinich’s voters, have come ahead of Edwards? If not, who would Dean voters have preferred? The younger and more charismatic Edwards, or the somewhat more historically leftish Kerry?

Does Queensland count? Geographically, we’re big of course, but you could hardly get less politically central :-).