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The Crossover Point II

John Rentoul

crossover 300x193 The Crossover Point IIOne 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:

Conservative 302
Labour 294
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 Partly it is to do with out-of-date boundaries, and David Cameron’s failure to ensure that Nick Clegg delivered new boundaries was one of the biggest political events of this parliament.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 Report

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  • Ciaran Goggins

    Gloat now that Farage and UKIP are torpedoed. They won’t recover from Newark. Did Steel cover up Cyril Smith’s sins?

  • newfriendofed

    I am not one for predictions but if it does turn out this way my hope is that the Liberals would balk at another coalition with the Tories and would go with Labour instead. I don’t think the country as a whole would find this as unreasonable as it would have done last time even if the maths made it possible.

  • Pacificweather

    For the reasons I have given before, the calculator is only accurate on 2010 figures. You could well argue that the voting pattern will be similar in 2015 for the same reasons as 2010 in which case the seat numbers could be very similar to those you have given. However, local factors (a change in regional bias, a particular local candidate, a large numer of candidates in a minority vote constituency, etc.) or a collapse in the LibDem vote in their core areas could change the picture given the 8 seat difference prediction between Labour and Conservatives. My guess is the LibDems will drop to 12% by 2015.


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