To reduce the need for tactical voting as far as possible, allow us to rank all candidates in an election and not just three.
Instead of just giving us three votes in a moderator election, give us as many as there are candidates (after the primaries). As an equivalent alternative, give us one vote less than there are candidates.
To avoid confusing voters into thinking that they must rank all candidates, leave an appropriate instruction, e.g.:
You can rank as many candidates as you want. If you do not assign the lower ranks, this may lead to your vote not affecting the election as strong as it could. However, the lower the rank the less likely it is to actually affect the result.
Do not label the voting buttons 1st choice, 2nd choice and so on, but rank 1st, rank 2nd and so on.
Finally, as an optional icing on the cake, implement the equal ranking of candidates (which is possible in STV; just split a vote), so I can express opinions like:
A > B > C = D = E = F > G
- I rank candidate A first,
- I rank candidate B second;
- I cannot decide which of the candidates C, D, E and F is better;
- but they are all better than candidate G.
If a voting system awards tactical voting, this is a bad thing as it means that voters who just vote by their actual preference are disadvantaged and the results may be warped due to a complex meta game arising from how voters expect other voters to vote. For example a presumed underdog with enough actual support to be elected may not be elected because people tactically do not vote for them to avoid wasting their vote on the underdog. On the other hand, if there is more than one seat, a candidate who truly is everybody’s favourite may not be elected because everybody counts on enough other people voting for them.
One of the advantages of STV (the voting system used by Stack Exchange) is that it reduces the need for tactical voting (compared to more naïve voting systems). However, as we can only rank three candidates, voting is still more tactical than necessary. For example, I heard people say something along the lines of the following about the current Worldbuilding election (four moderator positions available; a lot of promising candidates):
Candidate X is a certain winner, so I won’t vote for him but rather try to determine the other three positions.
Allowing us to rank all candidates lessens the effectiveness of such a strategy (it cannot be eliminated entirely, thanks to the Gibbard–Satterthwaite theorem) and makes voting less tactical, more fair and the outcome more likely to reflect the voter’s will.
Note that you do not have to have four moderator position for this to make a difference. It already makes a difference as soon as there are more than four candidates.
Also see this question on Politics on how reducing the number candidates to be ranked increases tactical voting in STV.
The only drawback is that the voting process is more intimidating, but a solid explanation should ameliorate this.
A practical example
In the last Stack Overflow election (three moderator positions available), there were 4780 exhausted votes, i.e., votes which could influence the election, if the voters had made an additional choice (which they might not have been able to do due to the limit of three choices). That’s 17 % of all votes.
The last elected candidate (Madara Uchiha) won by a surplus of 144 votes over the first runner-up (Vinod Madyalkar). That’s 3 % of the exhausted votes. So, if only 3 % of the voters whose votes were exhausted had made an additional choice in favour of Vinod Madyalkar, he would have beaten Madara Uchiha in the race for the last moderator position.
(Note that I am aware that this is a little bit simplifying things as all those votes are largely fractional, but the argument is not affected by this.)
Another example is the 2015 Information Security election in which there was only one seat, yet 27 % of all votes were exhausted, a fraction of which would have sufficed to change the result.
"But I do not want to need to understand STV to be able to cast my vote!"
Don’t worry, this proposal is working for your wish, not against it. Tactical voting means that understanding the details of the voting system is necessary to give your vote maximum weight. This proposal tries to reduce tactical voting.