At 10pm on Thursday, May 7, a tremor started to shake the Labour and Liberal Democrats campaign teams. In stark contrast to every opinion poll published in the fortnight before the election – barring one by Survation giving the Tories a six point lead – the BBC and Sky's exit poll was predicting that David Cameron's party would secure 316 seats, making it the largest in the House of Commons.
Labour and the Liberal Democrats were stunned. Lord Ashdown told Andrew Neil on the BBC that he would publicly eat his hat if the exit poll was right. But the poll was broadly correct, even underestimating the level of Conservative support in England and Wales and of the SNP in Scotland.
By midnight the tremor had turned into a seismic shock as it became clear that the Tories were heading for an absolute majority. Labour was to lose Ed Balls, the shadow chancellor, while the Liberal Democrats were virtually wiped out with the loss of 49 seats, including those of Business Secretary Vince Cable and Treasury Chief Secretary Danny Alexander.
As the soul searching and hunt for new leaders among the main losers begins – with UKIP yet to make up its mind about whether it actually wants a new leader – the polling companies have been left struggling to account for their shocking failure to forecast the final result.
The reasons proffered have been many: the shy Tory effect, first proposed in 1992 when John Major confounded the polls by beating Neil Kinnock; that the main polling organisations now inaccurately sample voters online or over the phone; too much notice being taken of the primarily left-leaning 'Twitterati'; and how UKIP made more inroads into Labour's heartlands than it did in the Conservative shires.
We may never know the answer as to why the polls were so wrong. The British Polling Council has announced an independent inquiry into the "apparent bias" the polls showed against the Tories and will recommend changes to the way that they are carried out in the future.
But it is clear that something went very wrong for Labour which, until the 10pm exit poll announcement, was confident that there would be, at the very least, days of horse-trading ending in Cameron being ejected from No 10.
Some analysts have suggested that Ed Miliband's YouTube interview with the comedian Russell Brand alienated a large chunk of middle England while others point to his much - the so-called "Edstone".
Lynton Crosby, the Tories' pugnacious Australian campaign director, is in no doubt about what happened. He told the Telegraph: "It wasn't just Ed Miliband's Labour Party that revealed itself as out of touch and remote from the people who are the backbone of Britain. It was a failure for the Westminster-centric 'Eddie the Expert' and 'Clarrie the Commentator' who were tested and found wanting. It was as much a judgment day for them as Ed Miliband and they lost. Most went to Oxbridge, talk only to themselves, and last time they met a punter was when they picked up their dry cleaning."
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