Over the last year couple of years Labour’s lead has gradually been whittled away, from ten points in 2012 they are now holding onto only the very narrowest of leads, with many polls showing them neck and neck. At the same time we have seen UKIP’s support getting ever higher, with polls regularly putting them in the mid teens. One naive assumption could be that supporters have moved directly from Labour to UKIP, but in reality there is a lot of churn back and forth between parties. A political party could be picking up support from one group of voters, but losing an equal number of voters somewhere else. The voters now backing UKIP could be people who earlier in the Parliament were backing Labour, even if they didn’t vote Labour in 2010.

Every month YouGov carry out around twenty polls for the Sun and the Sunday Times. In any individual poll the crossbreaks of 2010 Conservative, Labour and Liberal Democrat voters are too small to be robust, but by aggregrating up the polls from a whole month we have enough responses to really examine the underlying churn, and by comparing the figures from 2012 and 2013 to today, we can see how party support has changed.

All these charts are based on YouGov’s figures. For simplicities sake the movement between the parties are always *net* figures – for example, there are a very small number of people who voted Labour last time but said they’d vote Lib Dem this time, but the vast bulk of the movement is in the opposite direction. I’ve netted them up to get the overall movement between each party. I’ve also excluded very small movements made up of less than 0.2%. The percentages are of the whole of the sample, not of each parties support, and because the sample also includes people who say don’t know or won’t vote things don’t add up to 100%. You can click on each image to get a bigger, readable version. With that in mind…

Here’s October 2012, a high point for Labour when they were enjoying an average lead of around 10 points in YouGov’s national polls. Labour’s vote at the time was very robust, they were making a very small net loss to UKIP, but otherwise their vote from 2010 was solid and they had added to it small amounts of support from 2010 non-voters and Conservatives and a large chunk of former Liberal Democrats. Lib Dem support had already slumped, with the large majority of their support going to either Labour or to Don’t know/Would not vote (DK/WNV). The Conservatives had started to lose support to UKIP, but it wasn’t yet a flood – they were also losing some support to Labour and a large chunk to DK/WNV.

Moving onto October 2013, Labour’s lead had now fallen to around 6 points in YouGov’s national polls. They were still holding onto their 2010 support, but their gains from the Conservatives and non-voters were starting to falter. The movement of support from the Conservatives to UKIP had vastly increased, but part of this was balanced out by fewer Con-to-DK/WNV and Con-to-Lab switchers. The number of lost Tories was growing, but lost Tories were also switching their destination, saying they’d support UKIP rather than saying Labour or don’t know. The Liberal Democrats and Labour were also starting to see increased movement to UKIP, though at this point the big chunk of LD-to-Lab voters remained solid.

Finally here is the picture from October 2014. Labour’s average lead in YouGov’s polls last month was just 1.5 points and their retained support from 2010 is now faltering. In 2012 20.6% of our polls were made up of people who had voted Labour in 2010 and would do so again, that has now dropped to 16.6%. Those 2010 Labour voters are now flaking away towards UKIP, the Greens and the SNP. Movement from Con-to-Lab has now dried up completely. The chunk of CON-to-UKIP voters has continued to grow, but mostly at the expense of CON-to-DK/WNV, meaning Tory support has remained largely unchanged. Most importantly that solid block of LAB>LD switchers has started to wither, down from 6.6% of the sample to 4.6%. The Liberal Democrats themselves aren’t doing any better, but their former supporters are scattering more widely, moving to the Tories, UKIP and Greens.

Comparing the churn from 2012 and now you can see Labour’s issue. In 2012 all arrows pointed to Labour, they were picking up support from everywhere and holding on to what they had. Today they still have the benefit of a strong transfer from the Liberal Democrats (though even that’s declining), but they are leaking support in every direction – to the Greens, to UKIP and to the SNP.

One of the reasons the Conservatives ended up falling short at the last election was that they failed to clearly identify themselves as THE party for change – the public wanted rid of Gordon Brown and Labour, but following the debates Nick Clegg managed to make many people think the Liberal Democrats were the more convincing alternative. Ed Miliband may face a similar problem, the government still isn’t popular and still has a relatively low level of support, but the anti-government vote seems to be fracturing away from Labour to alternative non-Conservative parties like UKIP, the Greens and the SNP.

(This post is also featured on the New Statesman’s May 2015 here)