The general election in May is one of the most difficult to predict in British history. The result will undermine old certitudes. An incumbent’s share of the vote typically dwindles from one election to the next. An opposition has never won with Milibandite ratings on both the economy and the strength of its leader. Two-party politics, injured in 2010, could be confirmed dead in 2015. Six parties could have a critical role in deciding the allocation of seats. The 650 constituency races each have their own dynamic; it doesn’t make much sense to think of this as a single election.
Scotland is a case in point. Since the independence referendum on September 18, the Scottish National party has taken a big opinion poll lead over the Labour party: