Posts Tagged ‘mid-term blues’

The polling facts about Labour’s mid-term lead

09/01/2013, 12:02:49 PM

by Rob Marchant

Much has been made during 2012 of Labour’s solid poll lead, which has been of the order of 10% ever since the government’s disastrous Budget. For some it seems difficult to refrain from mentally converting this into a line on Peter Snow’s election night model of the House of Commons, showing a majority for Labour.

What this fails to account for, quite apart from the changed circumstances which may prevail in two years’ time (and which may be much more attractive for the Tories, as Peter Kellner cheekily points out here), is that incumbents tend to have a dip at mid-term anyway. Quantifying this effect would obviously help us to make more accurate forecasts, to the extent that this is possible.

Last week at Uncut, Atul Hatwal showed the numerical arguments against a win for any party which failed to establish a poll lead on the economy. In a complementary way, we can try and allow for this mid-term effect, to try and get a better idea of where things might end up, all other things being equal.

There are various ways of trying to gauge it*. A year ago, an excellent piece of analysis was carried out by Leo Barasi (and for which I am indebted to John Rentoul for pointing out) on post-war polls both eighteen months into a parliament and two years out from the next, which concluded, rightly, that Labour’s prospects were numerically better than many seemed to think.

Interestingly, this conclusion now looks a little less secure, not because Barasi’s model has changed or become less applicable, but because the polls have actually improved for Labour in the last year and therefore many commentators, who were very negative at the end of last year, have gravitated towards a much warmer view of Labour’s prospects.

To revisit the second part of that analysis – that of two years out from the next election – is now both timely and illustrative, which we do now in this graph:

It is interesting to look at the regression line but the data points, too, tell a story. It is also useful to apply a little political history to the figures.

First, the most striking thing to note is that over four-fifths of postwar oppositions have had a lead in the polls at this point, two years out from an election. Irrespective of whether they go on to win or lose. So having a lead in itself is hardly remarkable: in fact, allowing for outliers**, they almost all do. It is the size of the lead that counts. Conclusion: don’t get excited about being ahead in the polls at this point. It seems to be a necessary, not a sufficient condition. Not being ahead, now that would be something.


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