Read the full article http://yougov.co.uk/news/2014/06/16/how-lib-dem-prospects-affect-arithmetic-ve-day/
For each scenario, I show two seat calculations. In each case, the ‘uniform swing’ figures show what would happen if the percentage movement of votes were the same in every constituency. I have used the calculator provided by my colleague Anthony Wells’ Polling Report website.
The ‘adjusted’ figures show my best guesses of what would actually happen with these voting percentages. They vary from the ‘uniform swing’ figures in two ways. First, I assume that the personal following of Lib Dem MPs will help the party to retain eight seats it would otherwise lose – five to the Conservatives and three to Labour. Second, I assume that first-time Tory MPs will benefit from a ‘sophomore surge’ – just as Labour MPs elected for the first time in 1997 held more seats in 2001 than would have been expected on the national 2% swing to the Conservatives. (For a discussion of this phenomenon, see my blog earlier this year here). For the purposes of this analysis, I assume this is worth 18 seats to the Tories – seats they would lose on a uniform swing but in practice keep.
The combined effect of these two adjustments is to add 13 seats net to the Conservative tally and 8 to the Lib Dems, and cost Labour 21 seats. (I assume that UKIP will subside to around 10% and not have any MPs in the new Parliament.)
|Lib Dem Meltdown||Lib Dem Recovery|
|Vote %||Uniform swing seats||Adjusted Seats||Vote %||Uniform Swing Seats||Adjusted Seats|
|2% Con Lead|
|Con, Lab Level|
|2% Lab Lead|
1. The geographical bias in Labour’s favour largely disappears. Suppose both Labour and the Conservatives win the same number of votes. On a uniform swing, Labour would have either 35 more MPs (in the case of a Lib Dem meltdown) or 44 (Lib Dem recovery). But the adjusted figures reduce Labour’s lead to one (meltdown) or ten (recovery).
2. Labour must also abandon its hopes of winning an overall majority with a narrow lead in the popular vote. Depending on Lib Dem performance and the precise size of the Tories’ sophomore surge, Labour’s lead needs to be at least 3% and possibly 5%.
3. Conversely, the Tories could win enough seats to govern alone with a lead in the popular vote of just 2% (Lib Dem meltdown) or 4% (Lib Dem recovery). Such leads would not give the Conservatives the 326 seats they need for an overall majority, but enough to exceed the combined total of Labour and Lib Dems seats – the minimum that they will probably need to run a one-party minority government, at least for a while. (For those interested in the minutiae of these things, I assume that Northern Ireland’s 8-9 Democratic Unionists would support a minority Tory government in a confidence vote, while the Green, Scottish National and Plaid Cymru MPs would not.)
I would add a fourth conclusion, though this is more speculative. Let’s suppose Labour and the Tories enter next year’s election campaign level-pegging on 37% each, with the Lib Dems languishing on 8%. Then, on my adjusted figures, the contest to be the largest party will be too close to call.