But expressing your preferences doesn't actually accomplish anything useful.
You can do it, but what does it get you?
Instant runoff is not monotonic: there are times when the best strategy is to vote your favored candidate second and your second choice first so that the second choice can push out your least favored candidate.
I still find the nonmonotonicity of instant runoffs problematic. Something seems wrong about a system where you can lose by gaining votes. I'd expect instability to be higher than a similar system that is monotonic.
I agree with what /u/zestyping says in the other comment, so I won't repeat it. But here's a video explaining the strategic voting issue: https://www.youtube.com/watch?v=JtKAScORevQ
I've seen some voting systems include a "delegation" feature, where instead of submitting a full ranking of candidates (or whatever), you can just vote for a single candidate and your full ballot will be determined by their full ballot. What you're describing seems to be basically IRV but where you are forced to delegate?
(OK, I guess the runoff isn't truly instant, but still.)
I worry that this might have the same sort of monotonicity problems as IRV normally does, only in terms of the candidates' ballots instead of the voters'.
I know I've "voted defensively" before, and I really don't like having to do it. I want to vote for those that I agree with, I don't want to vote against those who I disagree with.
It may seem like a small distinction, but if someone loves candidate A, but they are extremely unlikely to win, most will end up voting for B because they REALLY don't like C.
That leads to A never getting in office until they become more like B.
But with instant runoff, I'm free to know that I can vote for A first, and B second, and not worry that my support for A is implicit support for C.
It not a perfect system, but IMO it's a lot better than what we have now in the US.
Edit: another piece that I forgot to mention is that instant runoff can give more signals beyond the winners or losers. Currently you have no way outside of polling to understand what voters want, it leads to a vocal minority being able to control the narrative.
With instant runoff, the runners can easily see that even though candidate A didn't win, they did get a sizeable number of votes, and maybe next time B runs, they will incorporate some of A's ideas into their campaign.
These charts[0], which I did not create, should explain why instant runoff voting is less than ideal. In particular, its nonmonotonicity (a candidate getting more votes can cause them to lose) is problematic, IMO.
Instant runoff is subject to the "Favourite Betrayal" problem, where placing your favourite first can lead to your second choice being eliminated before your vote for them can count in a later round.
Your example assumes people will vote for their second choice when it counts against their first choice. Most people won't, so approval often wont' work. Runoffs or instant runoffs are better.
I'd argue that instant-runoff is _worse than plurality_. It complicates the voting system, makes the wrong tradeoffs (lack of monotonicity is a very serious one), and I'd really like to hear more about why you think approval voting is worse than runoff (instant or otherwise).
Instant-runoff voting can punish voters for prioritizing a 3rd party candidate. IRV does not satisfy the monotonicity criterion. See this article [1] for more information.
In general, IRV is a poor system that is almost as bad as plurality voting in terms of how the outcomes reflect the voters' preferences (plurality voting is what the United States uses for most elections).
There are many systems that are better than IRV or plurality. I like approval voting [2], which is a system where you can vote for any number of candidates (instead of one candidate like plurality). Unlike IRV, you don't rank your choices. Approval voting is very simple (the simplest option other than plurality) and produces good outcomes.
Monotonicity intuitively seems like it would be desirable, but I'm struggling to see how the effect described in the video actually matters in practice. It seems vanishingly unlikely that candidates 2&3 would be eliminated in a tie (and you can just change the rules to force a re-vote/runoff in that case if you really think it's a bad outcome, similar to how you'd handle a tie in FPTP). And even then, the outcome of picking the first candidate when 2&3 are tied doesn't seem explicitly unfair. I'm sure there are other cases where this can show up too though, and maybe some of those do seem unfair.
I can see how ex post, one could say "if I had ranked my choice lower, they would have done better", but it's not clear to me that this property actually informs any real-world voting strategy ex ante.
Basically, this seems like a somewhat academic property that most voters probably wouldn't care about, so it's not clear that a lack of monotonicity would actually impede IRV from popular acceptance.
Instant runoff voting has the problem of nonmonotonicity. A simpler ranking system without rounds of elimination and vote shuffling would be better, IMO.
I used to support instant runoff voting. In fact, I voted to change the UK voting method to instant runoff in the 2011 UK Referendum.
However, I've become less enamoured with it. People don't understand it. It's used in London for the mayoral election, and people just get confused - they'll tell me they are putting the same party as their first AND second choice.
In fact, judging from the mayoral election, it wouldn't change much - the two main parties still end up getting the lion share of the first round of voting, which implies that the vast majority of people are loyal to those parties (a bit like football teams) and aren't voting for them out of tactical necessity.
I'd still go for instant runoff in a heartbeat, but it's not the panacea I thought it was.
I think instant runoff voting is optimal, but it's too confusing for an idiot in a hurry. I'd be content with simple approval voting. Every candidate has a checkbox next to their name on the ballot. If you approve of the candidate, check the box. Most checks wins. Ballot will have a lot of names, but that's the price of democracy.
I'm continually upset and confused by Instant runoff voting's popularity. IRV is, by my reckoning, a much inferior (and more complicated) system than other systems, like range voting or ranked pairs. And it has some bizarre properties that make me wonder if it is even worse than the traditional first-past-the-post.
One property of IRV that makes it so questionable is its non-monotonicity. This means that you can help a candidate by ranking them lower, and hurt a candidate by ranking them higher. It is extremely easy to visualize how ill-behaved IRV is in the charts on this website:
Meanwhile, ranked pairs (a "condorcet" method) has the property that, if candidate A is more popular than all other candidates pairwise, then candidate A will always win. This is _not_ true in IRV.
If you're interested in falling down the rabbit hole of electoral systems, I recommend looking at this chart that compares their properties:
Instant-runoff is a terrible voting system and should never be used, see http://zesty.ca/voting/sim/ . Approval voting is simpler and better. Condorcet is best except that it is somewhat complicated.
> Instant-runoff voting (used in practice for counting RCV ballots in the US) actually satisfies the "later-no-harm" criterion[0] of voting systems (unlike Approval Voting)
This is a flaw for instant runoff voting at a benefit for approval voting.
In a nutshell, later no harm means voting for your second can't hurt your first. But it can also mean that your vote for your second can't hurt your third either. Thus if it's more important to target your third than your first, you want to hoist your second favorite into the first position by burying your true favorite. That can never be strategically good with approval voting.
You can do it, but what does it get you?
Instant runoff is not monotonic: there are times when the best strategy is to vote your favored candidate second and your second choice first so that the second choice can push out your least favored candidate.
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