Trouble in the marginals...

A new poll out today confirms the scale of the task in Labour held marginal seats. The seats that David Cameron must win if he is to overhaul the 117 seats needed to get a majority of one.

The poll underlines the irrelevance of the national polls. It states the obvious, but it's important to underline the fact that David Cameron has to win in seats where Labour has held high levels of support since 1997 and, more often, since 1992. Areas that have got used to returning a Labour MP for four elections.

The polling suggests that in many of these constituencies - principally in the North - the Conservatives have an estimated 5.5% swing from Labour to Conservative. Put crudely, this will only be enough to secure around half of the seats (principally in the South East) in their target list of 117. The seats requiring a swing of more than 5.5% are mostly in the North... places like Bury, Warrington, Dudley. And they need them all to win. No question.

To get an overall majority the Conservatives need a swing of 6.9% in marginal seats, so this shows them falling short. The topline figures for voting intentions in these seats are CON 38%(+1), LAB 41%(nc), LDEM 11%(nc). To put that into context, for this particular group of seats (I assume by design rather than co-incidence) the required 6.9% swing equates to the two parties being exactly neck-and-neck. So in theory, if the Conservatives are ahead in MORI’s marginals surveys, they should have an overall majority. In practice of course that assumes Lib-Dem marginals behave the same as these ones, which is somewhat dubious assumption, so in reality the Conservatives could need a bigger or smaller swing against Labour, depending on how they do against the Lib Dems.

Election nights always surprise. But it just doesn't look possible that the Tories will win all those seats. It convinces me to scale back my prediction into Hung Parliament territory. The Great Unknown (never mind the Great Ignored) is Labour turnout and whether the Lib Dem vote or expenses fury to "Other" candidates takes votes off the Tories in those marginal seats, snatching their precious marginal wins from their grasp.

PREDICTION: Conservatives 4 short of a majority.