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Strategic Voting is any time you vote in a way that is not in line with your sincere preferences, in order to obtain a better outcome. Strategic voting can come in several forms.

Favorite Betrayal is when you vote against the candidate you like the most. Dude. You betrayed your favorite candidate? That sucks! Some voting systems, including the one we use today, as well as IRV, incentivize some voters to vote against their true favorite in order to prevent the election of a worst possible candidate (the greater evil). In Plurality voting, this known as the Spoiler Effect. The video below shows how this problem manifests in IRV:

In Score Runoff Voting, unlike IRV, for your honest vote of maximum favorite support to create your worst outcome, your vote would have to knock a ‘more viable’ candidate out of both of the top two scoring spots. SRV's runoff acts as a safety check on the outcome: It is vanishingly unlikely that the third place scoring candidate would actually beat both the first and second place top scorers in head-to-head matchups. It's actually very likely the top scoring candidate overall wins the runoff step.

Supporting the Weak Opponent is where you help out some weak candidate you don't like in order to disadvantage a candidate you think can beat your favorite. Some voting systems can incentivize voters to support a weak opponent, in order that their preferred candidate win the general election. In an open partisan primary election, for example, this is a viable strategy. If your party candidate is a shoe-in to the general election, you may cast a vote for the weaker opponent candidate so that your candidate has an easier time winning.

This is not a safe voting strategy in SRV. It is only viable if you have a very high degree of confidence that your favorite candidate will out-poll the strong opponent in the scoring round. Voting insincerely does not change the calculus between the your favorite and your strong opponent, but actually increases the likelihood that your favorite will get squeezed out.

Tactical Minimization is where you decrease your support for candidates other than your favorite. Score voting systems are said to encourage tactical "bullet voting" - supporting just one's favorite candidate and dishonestly voting 0 for all the others in order to give the favored candidate the best chance of winning. SRV's runoff step corrects for this strategic distortion in two ways: first, by incentivizing voters to differentiate scores of multiple candidates to have a meaningful say in the runoff, and likewise amplify, to parity, the preferences of those who do not bullet vote in the runoff step.

Tactical Maximization is where you increase support for candidates other than your favorite because you think your favorite is weak or you want to hedge your bet. In addition to the folks who say Score Voting systems are vulnerable to strategic "bullet voting", there are those who say the optimal Score vote is pretty much the opposite: that voters will gain strategic advantage by maximizing support for one perceived front runner and all the candidates the voter likes more than that one. As above, SRV's runoff step corrects for this strategic distortion in two ways: first, by incentivizing voters to differentiate scores of multiple candidates to have a meaningful say in the runoff, and likewise amplify, to parity, the preferences of those who do not maximally vote the top two in the runoff step.

In Summary, while no voting system entirely eliminates the tendency for voters to try to "game the system", Score Runoff Voting both minimizes tactical voting and corrects for its distortion in the runoff step. Since Score Voting with honest voters is tops for maximizing Voter Satisfaction Efficiency, adding a strategic incentive for honest voting is a huge win.

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  • commented 2016-12-09 12:49:13 -0800
    On bullet voting in score, although this is possible, I find the arguments not entirely convincing. It’s just as reasonably strategic to vote one candidate top score and all others zero as it is to do all you can to stop a bad candidate by voting them zero and everyone else top score. Likewise, there’s a perfectly sensible strategy to giving mixed scores to middle candidates. After all, you have an interest in both your favorite(s) winning and in the worst candidate(s) losing. So, it’s likely for strategic score voting to include multiple high and low scores and some middle scores.

    Nevertheless, it’s true that score runoff provides an extra balance against strategic voting, at the cost of a just little extra complexity that is easy enough to understand and helps satisfy those who like rank voting. SRV seems the optimal balance.
  • commented 2016-12-09 12:38:32 -0800
    Well put. The primary thing for everyone to realize is that honest score voting is far and away the best possible voting system, there’s just no way to enforce honesty. But if we minimize the impact of dishonesty, then we’ve got about as good as can realistically be achieved.

    We need more real-world experience to say for sure, but there’s lots of reasons many voters will be honest. People like passing judgment. Score voting, unlike any form of rank, allows people to register their disapproval as well as approval, not only their relative preferences. I’m sure there’s a self-selection where those interested in studying voting are also those most likely to consider strategic voting.