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Polling Observatory #11: When is a tie not a tie?

This is the eleventh of a series of posts that report on the state of the parties as measured by opinion polls. By pooling together all the available polling evidence, we can reduce the impact of the random variation each individual survey inevitably produces. Most of the short term advances and setbacks in party polling fortunes are nothing more than noise; the underlying trends – in which we are interested and best assess the parties’ standings – are relatively stable and little influenced by day-to-day events. If there can ever be a definitive assessment of the parties’ standings, this is it. Further details of the method we use to build our estimates of public opinion can be found here.

“Prediction is very difficult” Niels Bohr wrote once, “especially about the future.” Over Christmas, we wrote that the polling boost Cameron’s Conservatives received following the EU summit “veto” might prove fleeting, as voters’ attention returned to the bleak landscape of domestic politics. Our latest estimates defy this prediction, with the Conservatives continuing to poll above their 2011 averages in the New Year. Our estimate of Conservative support for January 2012 is 37.7%, up 0.3 points from last month and close to 4 points above the low points of 2011. Labour’s estimate stands at 37.8%, down 0.8 points from last month. For the second month in a row the two main parties are in a statistical tie. The junior partner in the governing coalition, the Liberal Democrats, continue to flatline below 10%. We have them at 8.6% this month, down 0.2 points on last month.

Cameron’s resurgence in the polls, and Ed Miliband’s continued struggles, have lead some commentators to speculate about a possible Conservative majority at the next election. This is premature. Although the two parties are level pegging in the polls, the Conservatives continue to suffer a handicap when votes are translated into seats at Westminster. Estimates from the Electoral Calculus website suggest that at equal vote shares of 38%, the Labour party would be 38 seats ahead of the Conservatives, and only three seats short of an overall majority. The Conservatives need a lead of 3-4% in votes in order to draw level in seats, and a lead of 7-9% in order to achieve a majority of one seat. So, in other words, drawing level in votes is not enough for Cameron’s Conservatives: they need leads close to double digits to be confident of securing an outright majority.

Why does the electoral system put the Conservatives at such a disadvantage? As detailed by Michael Thrasher and colleagues in a recent article, the main advantages to Labour are the result of the geographical distribution of its support, and variation in turnout between constituencies. The geographical effect comes about because Conservative votes tend to be concentrated in constituencies with very large Conservative majorities, while Labour votes are more evenly spread across the seats Labour win. This means less Labour votes than Conservative votes are “wasted” just to add to already large majorities in already safe seats.

Also, turnout tends to be higher in Conservative held seats than Labour held ones, so even if both sets of constituencies have equal number of eligible votes, more votes are cast to elect Conservative MPs than Labour MPs, as in Labour seats fewer voters show up at all on polling day. A third, much smaller, source of Labour advantage is differences in the number of eligible voters in Conservative and Labour seats, which results both from constitutional legacies such as the over-representation of Wales at Westminster and from the continuous movement of voters away from declining, Northern, Labour voting regions towards expanding, suburban Southern seats which lean Conservative.

Many commentators have suggested that the boundary changes being brought in by the Coalition will “level the playing field” at the next election. This is unlikely. The boundary changes will only deal with the effect of uneven constituency sizes, which is a small contribution to the bias in the system. The much larger effects of uneven geographical distribution and voter turnout will remain. Loyal Conservatives in the shires are likely to continue dutifully piling up massive majorities for their local MP’s at the next election, and as a result Cameron’s party will continue to face a tougher challenge than the polling suggests.

Rob FordWill Jennings and Mark Pickup

Published inBritish PoliticsPolling Observatory

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