Will tactical voting shape result of the UK general election?

Tactical voting is one of the big themes in the 2015 UK election, as smaller parties emerge as players and their bigger counterparts battle to hold on to their seats. Around 8% of British voters tend to vote tactically – a figure that has been pretty stable since 1992. That equates to around about 2.3m people.

One reason to think tactical voting will increase in 2015 is that is there has been a rise in support for smaller parties that are particularly likely to come third or lower in individual constituencies, particularly UKIP and the Green Party.

In 2010 roughly 24% of voters were in this position. Now it looks more like 28%. So whereas there used to be about seven million voters who supported a party coming third or lower in their constituency, as many as eight million might in 2015.

The key issue for people thinking about voting tactically is always whether it is clear which two parties will come in first and second place in the constituency in question. They can then decide if they’d rather vote with the aim of keeping one or the other out of the seat than vote for the party they actually support.

But it looks like there will be a lot of change this time when it comes to which two parties will come top in different seats. About a third of the seats in England and Wales look like they will have a different pair of parties finishing first and second.

This mostly affects the Liberal Democrats – who are predicted to fall into third place or lower in a number of seats that used to put them in the top two. In 2010, the party was fighting the Conservatives in 26% and Labour in 15% of seats. Now candidates are more often watching from the sidelines as the battle for the top spot plays out.

A familiar sight in letterboxes in 2015.electionleaflets.org

A lot more classic Conservative-Labour or Labour-Conservative contests are expected this time. Last time fewer than half of seats had Con and Lab first or second, this time is looks like 80% of seats in England and Wales might be like this. Unless the Liberal Democrats got at least 30% last time, they are unlikely to be in first or second place this time.

Should you do it?

To check what the tactical situation is in your constituency perhaps the best resource is the London School of Economics' Democratic Dashboard. This website has the latest constituency polls, forecasts and previous results for each constituency as well as various other bits of useful information on each constituency.

While most seats in England will be Con-Lab or Lab-Con contests, if UKIP does as well as the polls suggest, and particularly if it campaigns effectively in seats where it already did well in local and European elections, it could come second in around 30 seats. Most of these will be Tory seats, but some Labour.

Supporters of parties likely to come third or lower in seats where UKIP are contenders are most likely to consider voting tactically for whichever candidate is best placed to beat UKIP. There has especially been talk of this for the main UKIP target seats, such as South Thanet where Nigel Farage is standing.

The SNP came third or lower in 24 of the 59 Scottish seats in 2010 but now pretty much every seat not already held by the SNP is a contest between the SNP and whoever won last time. If the polls are right, SNP supporters will never need to consider voting tactically because they will come first or second in every constituency.

The situation is more complicated for supporters of other parties in Scotland. Mainly it will be a case of considering whether you want to vote for the party that won last time. But again it is safest for supporters of unionist parties to check the tactical situation in the latest forecast.

Will it work?

John Curtice has estimated that tactical voting might save around seven seats from the SNP but not enough to stop the predicted landslide that the polls are suggesting.

And beyond the constituency strategic situation, it also matters how much voters care about the parties. UKIP voters often don’t care much whether the Conservatives or Labour win and so they are less likely to vote tactically for one over the other.

Similarly, it is not clear that Conservative supporters in Scotland are sufficiently more fond of Labour than the SNP to want to vote tactically to save the former from defeat at the hands of the latter. Green supporters, on the other hand, typically care enough to want to vote tactically for Labour (or even the Liberal Democrats) against the Conservatives.

So with more third-party supporters there is likely to be more tactical voting this time. But with such big changes in party support, the decisions are more complicated. We should not be surprised if there are also many tactical mistakes, with people deserting parties that actually end up coming second or even first.

Stephen Fisher has received funding from the ESRC and British Academy.