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Tactical voting: a very risky strategy in 2015

It’s hard to have a political discussion in Twickenham ahead of the election without the issue of tactical voting coming up. Especially, I suspect, as a Labour supporter.

To vote tactically you need to have an idea of how other people will vote, but are elections that predictable? More to the point, is this election that predictable?

In Twickenham there has been a proportion of people who would not normally vote Liberal Democrat but who have voted tactically for Vince Cable in an attempt to prevent a Conservative candidate taking the seat.

Since 1997 a Labour-leaning voter could be reasonably confident that many of their fellows would be voting tactically, and so they could do so with little fear of undermining their own candidate. It follows that over time this becomes apparent to more people, and so more people adopt this approach.

Everything changed in 2010. This is an image from may2015.com currently running a ‘poll of polls’ for GE2015. It shows polling data from the last election to 28th April 2015. Vote share for Conservatives (blue line), Labour (red), LibDems (yellow), UKIP (purple) and Greens (green).


In 2010 the Liberal Democrat vote fell off a cliff into single digits and hasn’t recovered. We all know why that is, but we also know that this fall won’t be uniform across the country, and especially not in constituencies with a well-known Liberal Democrat incumbent MP. Like Twickenham and Vince Cable, for example.

However, it does make it clear that we can’t use the 2010 election result alone to predict how people may vote in 2015. Two reasonable assumptions for this are:

  • Vince will have lost a proportion of his vote to people who voted Liberal Democrat through choice last time but who would not choose to support the party this time 
  • Vince has historically been supported by tactical voters who would not choose to support his party in a ‘free vote’, and they may be less inclined to vote tactically this time around due to his role in the coalition government, reasoning that this is effectively a vote for the Conservative party by proxy.

Anyone who has chatted to anyone in the area about the election will know that there are definitely people in both these camps. Tactical voting only works if a sufficient proportion of people engage in it, but will the tactical vote will turn up this time around?

More to the point, should Liberal Democrat-leaning voters consider voting tactically for Labour this time around to keep the Conservative candidate from taking the seat?

There’s generally very little data to base this on, but the Liberal Democrats kindly undertook a poll in the constituency last year. As Lord Ashcroft says, a poll is a snapshot not a prediction, and the point of referencing it here is to see what it can tell us about voting intentions at that time in contrast to 2010.

The ICM poll, reported here at the time, has the Conservatives in front with Vince behind and Labour in third place. Here are the results weighted for turnout reported on the BBC website.


If we plot the GE2010 results and 2014 poll results against time we see this.


The Conservative vote hasn’t shifted at all. The Liberal Democrat share of the vote has collapsed and the Labour vote has surged. This was a year ago, since when the Liberal Democrat vote across the country has fallen further and the Green vote has increased.

What this all implies is:

  • Conservative vote is relatively stable in Twickenham and has not picked up any ex-Liberal Democrat support. This is probably to be expected
  • Labour support in Twickenham is much higher than a simple glance at the GE2010 result would suggest. It’s hard to know whether this increase consists mainly of previous tactical voters or also includes new support
  • Vince Cable is not immune from the damage that has been done to the Liberal Democrat vote share as a result of the coalition government and may well lose his seat
  • The tactical vote in Twickenham cannot be relied upon to materialise this time around

Many people we have spoken to have said that they are angry or disillusioned about their previous tactical vote for Vince and won’t be repeating it this time. With the result this close people who have voted tactically for Vince before should know that this time there is no guarantee that their fellow voters will do the same. Therefore a tactical vote is very risky this year.

Two key objections Liberal Democrat supporters may raise at this point:

  • Private Liberal Democrat polling which names the candidates on the ballot paper tends (according to the LibDems) to produce a better result for incumbent Liberal Democrat MPs. Whether this means they have a better predictive power remains unknown and is not really the point here, as we’re not making any predictions. The point is that Vince Cable in Twickenham is not immune from either a fall in ‘natural support’ or tactical support, and this fall has made it hard for him to retain the seat
  • Local elections took place shortly after this poll in which Labour received a significantly lower vote share. It’s hard to see this as relevant as people often vote differently in local, European and General Elections (see results for UKIP last European elections). We’re not aware of any forecasters currently using local election results as weighting for constituency level predictions for GE2015, although it’s possible that more complex models do have some weighting for this. In any sense, local elections are very low-key events with a generally low turnout and a General Election dominates the domestic news agenda for months and involves all aspects of people’s lives so it’s hard to see how these are comparable events

In conclusion, from looking at the numbers and speaking to local people while canvassing it seems very likely that many people who previously gave Vince a tactical vote are now looking to back Labour or the Greens at this election. If you feel minded to back a candidate other than Vince then it’s important to know that the tactical vote may not materialise this year. This time we will be voting for what we believe in and a vision of the country we want to live in. We hope that everyone will do the same.

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