National opinion polls ahead of the 2015 UK general election have remained static for months. They’ve typically reported that Labour and the Conservatives are tied on 32-35% of the vote each, that UKIP and the Liberal Democrats have around 13% and 8% respectively, and that the Greens and the SNP are both hovering around 5%. This has prompted some analysts to ponder whether these polls are really telling the whole story. Lord Ashcroft – one of the most frequently cited pollsters – has labelled national polls mere “mood music”, and has been conducting additional polls at the constituency level in order to better predict how many actual seats each party can expect to win.

Our approach – which is based on using data from Twitter to make faster and more accurate predictions of the vote share – also allows us to paint a more detailed picture of the election than the national polls imply. It allows us to spot changes in the public mood early on, as well as the more subtle fluctuations that averaged national polls might paper over. Ultimately, we hope that properly understanding these shifts will help us to make better predictions – particularly if they occur just before polling day when much opinion polling will have stopped.

What’s our data telling us at the moment? Throughout the election period, the Conservatives have been more commonly referred to than any of the other parties, with around 40% of all tweets about the election referring to them in some way. Labour are in second place with around 30%. UKIP and the SNP are in third and fourth with 17%, and the Lib Dems and the Greens fifth and sixth with about 7%.

However, the way in which these numbers have changed over time is likely to be more revealing, as this may indicate a change in the public mood. Though there were brief peaks when each of the parties launched their respective manifestos, this pattern has held surprisingly well. Until recently, that is, when Labour overtook the Conservatives for the first time. As our charts (and the image above) show, this shift coincided with the broadcast of the BBC’s Question Time: Election Leaders Special, and occurred shortly after Ed Miliband was interviewed by the comedian and activist Russell Brand.

Of course, parties can be referred to in both a positive and negative sense, so just looking at the number of tweets may be misleading. Using an approached based on automated sentiment analysis, we are able to look at just those tweets that express positive sentiment. If we do this, we see that throughout the election period, positive tweets have most often referred to the Green party, with the SNP in second place, and the four other main parties closely bunched together behind them.

Interestingly, if we look at the chart showing just the positive tweets referring to the Labour party, it could suggest that the recent rise in the total number of tweets is driven by positive sentiment towards them. Could this be the early signs of a shift that is only reflected in the opinion polls later on? Time will tell.