On the face of it, tactical voting seems straight forward. If the party that you really want to win doesn’t stand a chance of winning in your consitutency, then under the First Past The Post electoral system, if you want your vote to make a difference, you should vote for a party that does stand a chance of winning. Ideally, the one that you like the most out of the plausible options, or at least, the one you dislike the least.
When you unpick the assumptions in this, this is where things start to get tricky. How do you know which parties stand a chance of winning? Prevailing wisdom is that it’s between the incumbant and the party that has come second. But this already falls apart where there are multiple challengers with similar vote amounts (such as in a three-way marginal).
We should question the assumption that the party who is currently in second is the party to tactically back.
Let’s consider a simplified model of there being only three parties: the Conservatives, Labour and the Liberal Democrats. With a broad brush stroke, we can paint those three parties in differing positions on two axes: social progressiveness vs social conservatism, and free market vs state control. (There are many other axes that can be considered, but keeping it at 2 keeps the example simple, and the principles the same). We can portray the Conservative party as pro-free market and socially conservative; Labour as pro-state control and socially progressive; and the Liberal Democrats as pro-free market and socially progressive. (Once again, these are very broad brush strokes).
An individual voter will have different beliefs along those two axes, and also have different weightings as to how important those beliefs are to them (for example, I’m generally pro-market and socially progressive, but would weight social progressiveness much stronger). If a voter that would otherwise pick the third party believes that the choice to be made is between the first and second party, then they will often tactically vote between those two. It’s important to remember that tactical voting goes both ways. Some third party voters might actually align closer with the incumbant, and choose to vote for them. Others may vote for their preferred party anyway, even if they’re not perceived as a challenger (purely to make a statement in terms of national polling figures, or because they at least want that candidate to retain their deposit). Sweeping statements made by runner up parties such as “if all the voters for the smaller parties switched to us, we would win” might be true, but actually unlikely, and are about as helpful as “if everyone who didn’t vote last time voted for us, we’d win” (which again assumes that the people who didn’t vote would vote for you). If a minor party chose to stand down in an area, there’s no guarantee their votes would all go to the runner up, or that they’d even vote at all.
The other thing to bear in mind is that tactical voting is not a new phenomemon. People will have voted tactically in previous elections, if they would otherwise support a party not perceived as a realistic challenger. There may not be many voters left who vote for the other smaller parties who can be “squeezed” to vote for you as runner up, therefore you may never be able to grow your vote to go from runner-up into winner. This is especially true if the runner-up has been consistently runner-up for years, and never been quite able to unseat the incumbant.
Which brings us back to the number one problem with tactical voting: you don’t always know who the best challenger party to get behind is. It’s not always the previous runner-up, if that runner-up is unable to squeeze any more votes to take them into winning place.
What if the party that is currently in third place was the real challenger? Even if they’re far behind now, could they ultimately gain enough to win and unseat the incumbant? If they were seen as a challenger, we can assume they would first win back all the voters that prefer them but currently tactically vote away from them (in both directions, both for the incumbant and the runner up), and tactical voting would move in a new direction. Instead of tactical voters for the second party coming from the third, voters for the second party could choose to tactically back the third party (of course, some might choose to tactically back the incumbant, if they’d rather the incumbant win than the third party). In this configuration, the third party might actually win, and actually be the real challenger, as they could actually “squeeze” enough votes to win.
How do we know if the third party is the real challenger or not? That’s the tricky bit. Constituency polling can help us here, by proposing hypotheticals of asking how you would vote if the previous runner up was actually the third party.
You may have seen when the North East Somerset Lib Dems did this (and sadly it showed them still unable to beat the Tories to unseat Rees-Mogg), and it was wildly condemned as being misleading (there was a lot of nuance in the small print).
In another real world example, let’s look at the City of London and Westminster. In 2017, the Conservatives won with 46.6% of the vote, with Labour in second with 38.4% of the vote. The Lib Dems came 3rd with 11%, which is quite a way behind. Conventional logic would suggest a gain of 36 points in one election would be an unrealistic ask.
However, this seat has been Conservative since its creation in 1950. This suggests that maybe the hypothesis before about the runner-up party (Labour) reaching a peak and being unable to squeeze any more votes, despite being not really that far behind (only a few thousand votes), may apply in this case. Deltapoll have done polling, asking how people would vote if the Lib Dems were seen as the challenger party, rather than Labour. This polling suggests that if this were case, the Lib Dems would win a majority, with 51% of the electorate voting for them (a comfortable margin over the Tories). That’s a hell of a swing, but really demonstrates the hypothesis I put out above: Lib Dem voters are already tactically voting Labour in large numbers in this constituency, and Labour voters would switch to the Lib Dems as a tactical vote. And if they did, they’d unseat another Tory (and the current polling landscape looks like depriving the Tories of a majority is the most realistic outcome progressive parties can ask for).
The City of London and Westminster isn’t the only one, The Observer have done some similar analysis on a number of marginal seats and have come up with some what might seem surprising suggestions, although hopefully now make sense in context of the hypothesis laid out above.
The problem then comes to explaining this concept, and convincing voters that the third party might actually be the best chance to get behind to unseat the incumband. The explanation of “previous runner up being best challenger” seems simple, but isn’t always true, because of the hidden complexity of FPTP. And trying to convince voters of a complex message, versus a simple, but wrong, message, is tricky.
The fact that tactical voting is needed at all is a failure of the British electoral system. Asking people to vote for not who they want to win, but who they dislike least out of the parties that may possibly win, without knowing for sure who the parties that may possibly win is, is overly complex and unfair. FPTP’s method of simply placing a X next to one candidate seems simple on the surface, but is actually complex. Alternative systems, such as instant runoff voting, allow users to rank their choices, knocking out a candidate that comes last in a round and then re-allocating the votes that that person had, essentially letting you express a first preference, and then tactically vote if that first preference never stands a chance. Ranking candidates seems more complex, but is actually simpler for the elector than making guesses around tactical voting under FPTP.
If there’s anything that the discussion around tactical voting in this election shows, it’s that electoral reform in the UK is needed.
As full disclosure, I’m a member of the Liberal Democrats, which is a party that would stand to benefit under a change to the electoral system.