When voting systems are evaluated, tactical voting is considered a problem. I agree to the extent that an average voter has enough information to successfully tactically vote. For example, in a FPTP election, I can look at any poll and realise that my preferred third-party candidate has no chance of winning and redirect my vote to one of the more popular candidates.

But in any more complex system, a particular tactical vote seems like it's only actually tactical if you have a lot of knowledge which in my experience as a voter isn't typically available.

In a simple example of single transferable vote, let's assume there are three parties, left (L), centre (C), and right (R), and all voters for (L) and (R) give their second preference to (C), and voters for (C) give their preferences equally between (L) and (R). Let us say that the voting proportions are roughly L = 40%, C = 30%, R = 30% according to a poll. If my preferred candidate is (L), I could tactically vote (R - L - C) to "ensure" that (C) is eliminated first, ensuring that (L) receives 15% extra from (C)'s preferences, and defeating (R) by 55% to 45%. This would be better than if I voted (L - C - R) according to my true preference, because then (R) might be eliminated first, allowing (C) to defeat (L) by 60% to 40%. All power to the tactical vote.

But real life is much more complicated. I can't really trust the poll, and maybe the difference between (L) and (R) is a little less, and the voters from (C) are leaning a bit more to (R). For all I know, my vote might well allow (R) to actually defeat (L) and win the election. Especially if I consider that other people might be tactically voting. This is surely relevant: whether to tactically vote depends on how many others will be tactically voting (and which way).

Given this, why is the theoretical of tactical voting under perfect information considered such a big deal? I would be interested in evaluating a voting system by, for example, whether if you could estimate the likely outcome to within 4%, is tactical voting still possible. To me, as a lay person, that would meaningfully illuminate differences between systems, but I can't find evaluations of voting systems according to these criteria. So my secondary question is, do such assessments exist?

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    I'm not sure tactical voting is considered important. Most of the things I read in this area are concerned with creating a system that doesn't ask people to vote tactically, but to vote for what they actually want as that is the best way to actually give people democratic power.
    – Jontia
    Jul 2 at 9:45
  • At the final European Parliament election in the UK prior to Brexit, I was in a 6-member d'Hondt constituency, and I did successfully predict from published opinion poll data which parties would be the top two competitors for the 6th and final seat, and therefore which two parties one would need to choose between for an effective tactical vote. It was a bit fiddly, but not particularly difficult with access to a spreadsheet. Jul 7 at 16:41

I would challenge the premise that is something inherently wrong with tactical voting in the first place. Or that it is difficult to figure out how to vote.

My own positions - order does not mean weight I attach to them - would be:

  1. free market
  2. socially liberal
  3. very concerned with global warming.

Yes, there might very well be an election where a candidate happens to rate strongly on all 3 items. And that would make them my preferred natural candidate.

However, as #1 tends to play really badly with #2 and #3, at least in the views of voters, I know this will never be a winning platform, so my vote for this particular candidate will be wasted. Therefore I will switch my vote to someone else that is acceptable on #2 and #3 and not a complete disaster on #1.

I don't need any great amount of special information to arrive to this conclusion. And I don't believe I need condescending special electoral rules to tell me I am "doing it wrong" or am being manipulated either.

Note that this whole concern with tactical voting is somewhat in contrast with the 2020 POTUS election where, by and large, center and left of center voters were advised not to vote for any third party as that would, in essence, be an extra vote for Trump. Again, not particularly rocket science to get at.

I might be an outlier in my preferences, but in practice, many voters have reasons to pick not their special rainbow unicorn but someone acceptable who is likely to win.

Of course, someone who works professionally to redraft new voting procedures to replace a basic voting system with one of the more exotic variants will have an entirely different point of view and that has to be taken into account when following their analysis.

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