The Crossover Point II
One or two comrades have yet to catch up with my Four-Square Rule, which is that the Conservatives need to be four points ahead in percentage share of the vote to be the largest party in the election next year. As I said on Sunday, that, rather than the point at which the Tories simply move into the lead in the opinion polls, is the true “crossover point”.
Some carpers demanded to see my working.
I refer to the Electoral Calculus website, which allows you to play around with the numbers. I assume that the Liberal Democrats will get about 12 per cent of the vote next year (half what they got in 2010) and UKIP will get about 10 per cent (up 7 points from last time).
However, the Lib Dems are good at defending seats they already hold and so I assume that, in the seats that matter, they will do as well as if they were polling 15 per cent nationally. As UKIP is likely to win either one seat or none, I have assumed that their vote is 7 per cent for the purposes of these calculations (you could re-do them with UKIP on 10 or even 15 per cent and it would make no difference).
If we put Labour 33½% Conservative 37½% Lib Dem 15% UKIP 7% into the calculator, it produces this outcome in seats:
Lib Dem 27
For a Commons majority, the Tories need to be about seven points ahead, while Labour need to be only one point in the lead.
I won’t go into the reasons for the apparent bias in the electoral system here. I have done it before. Partly it is to do with out-of-date boundaries, and David Cameron’s failure to ensure that Nick Clegg delivered new boundaries was one of the biggest political events of this parliament. But mostly it is to do with Labour and Conservative voters behaving differently. Tories tend to turn out everywhere, even in safe and hopeless seats; Labour voters are more likely to turn out in marginal seats, where their votes are more likely to make a difference.
Polling graph from UK Polling ReportTagged in: election 2015, opinion polls
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