Thank you for mentioning Instant Runoff Voting. I've been trying to get anyone IRL to have any interest in it at all. Even the third party nerds weren't interested even though it'd benefit them.
The best system seems to be approval voting. You just are allowed to vote multiple times if you want. And the candidate with the most votes wins like normal. See http://rangevoting.org
Your concerns just don't play out.
The problem with IRV is demonstrated in more detail here: https://www.youtube.com/watch?v=7Q7rzqJ0YS8
I think it's still better than FPTP, and it does let third parties at least get some attention. But there are other, better, systems. IRV has been adopted in a few places in the US, and then abandoned shortly after. I think systems like approval voting have a better chance of catching on.
But you can get more third party candidates winning (in single winner districts), leading to coalitions within parliament, which is probably what the parent means.
Of course most countries that have this system end up with regular coalition governments which is sometimes one criticism of the system. But surely a coalition working together as part of a parliament with at least three groups is better than two groups at perennial loggerheads with each other.
This only seems to lead to ever greater tribalism and us and them politics.
Unless I misunderstand IRV, there is no "vote stealing" due to your vote automatically dropping off to your next-preferred candidate.
> Eventually they would steal enough votes to cause them to be eliminated.
I assume by "them" you're referring to a (previous) major party. In that case, I don't see an issue at all. This will simply mean that the voters get better options and the top two parties will be pulled more towards the median at threat of being surpassed by a third party.
> And you get only 2 viable parties.
This either contradicts the first point or is completely meaningless. Of course there will be two top parties by definition for any specific election. However, IRV allows voters who align themselves more with a particular third party to show their support for that party without possibly spoiling their next favorite candidate and resulting in one they oppose winning.
I looked at your link, and I'm unconvinced by this argument that IRV is no better than FPTP:
> A lot of voters will, in an election like Bush v Gore v Nader 2000, exaggerate their good and bad opinions of Bush and Gore by artificially ranking them first and last, even if they truly feel the third-party candidate Nader is best or worst. They will do this in order to give their vote the "maximum possible impact" so it is not "wasted". Once they make this decision, in IRV, Nader automatically has to go in the middle slot, they have no choice about him. If all voters behave this way, then automatically the winner will be either Bush or Gore. Nader can never win an IRV election with this kind of strategic voters.
This seems to assume that voters will not understand how the system works. What reason would voters have to rank Gore over Nader when there is no risk of spoiling anything and having the candidate farthest from them win? It's not like the ranks are worth more or anything. I can't think of any situation where putting Gore over Nader would result in "maximum possible impact" compared to the opposite ranking. This whole argument just seems very silly and misleading.
It's true that IRV limits the cost of vote stealing. But first votes still matter a huge amount in IRV, and you can only give one first vote. So there can always be some vote stealing. This is not a problem when third parties are really small and inconsequential. But if this actually worked to create viable third parties that had significant percent of the vote (the main goal of people that want such systems, otherwise there is no point), it would become a huge issue.
The link I posted shows that approval and range voting do vastly better in computer simulations of elections. Which is nice because approval voting is much simpler. And there is never a scenario where you shouldn't vote for your favorite candidate, under approval voting.
The last issue has been experimentally observed in Australia:
http://rangevoting.org/AusAboveTheLine07.html
People insincerely rank the competing party in last place, even though they don't really think they are the worst party. The major parties encourage this, and explain to their voters how to vote strategically.
More issues here: http://rangevoting.org/IrvExec.html
>Unless I misunderstand IRV, there is no "vote stealing" due to your vote automatically dropping off to your next-preferred candidate.
The problem is that they drop to your next preferred candidate who has not been eliminated.
If you're thinking about the problems that occur with plurality voting, it's easy to imagine your second choice will always be a popular "safe" choice, but if third parties get stronger (which is surely the point?) those safe choices can end up being eliminated before your second choice can help them.