Although Eastleigh was dire for the Tories, most commentators were wrong in suggesting it was also bad for Labour's prospects at the next election. In fact, it confirmed why Labour can still win in 2015, despite its terrible defeat in 2010, because these are times that defy psephological orthodoxy.
First, the Tories took office on a historically low base for a governing party. Their vote had been stuck over nearly two decades, inching up painfully slowly from a dreadful low of 30.7 per cent in 1997, to 31.7 per cent in 2001, then to 32.4 per cent in 2005 and finally to just 36.1 per cent in 2010 – in government without having won. And that despite facing a Labour Party with an unpopular Prime Minister, which had lost trust, and which had carried the can for the worst global economic crisis for 80 years. Not only did the Tories fail to win, they managed to gain a mere five per cent in the thirteen years after their landslide defeat in 1997.
Furthermore, just 23.5 per cent or 10.7 million of the electorate actually voted for them. David Cameron became Prime Minister on a pitifully low base. Apart from when Tony Blair led Labour and despite a significant population rise in the meantime, Cameron achieved the third lowest number of Tory votes since 1931 and the lowest Tory percentage of the electorate since 1918.
Second, Labour under Ed Miliband has quickly recovered its natural vote which had, stage by stage, defected, in the main to the Liberal Democrats, after the introduction of student fees and, above all, the Iraq War. That vote felt utterly betrayed by the Lib Dem leadership’s enthusiastic embrace of a right wing economic agenda which makes Margaret Thatcher look moderate; it will very likely stay with Labour and not easily go back to the Lib Dems except, perhaps, as in Eastleigh, where Labour cannot win.
Third, and perhaps most importantly, the Tory-Labour duopoly of British politics seems broken. Since its high point in 1951, when 97 per cent voted Tory or Labour, it has collapsed to just 65 per cent – that nadir the culmination of a long trend in the rise of smaller parties, reflecting progressive disillusionment with British politics and declining turnout. UKIP's stunning performance at Eastleigh confirms that this will not easily be reversed.
Furthermore, in the past, people might only vote every four years in a general election and for their local council, often on the same day. Now there are five-yearly European elections, annual elections for multiple layers of local government in many parts of England, and elections every four or five years for devolved institutions in Wales, Scotland, London and Northern Ireland.
The more opportunities people have to vote for different bodies or posts, the more politically promiscuous they become. The Lib Dems have been the main beneficiaries but also UKIP, Plaid Cymru and the Scottish National Party. Once people break the habit of a lifetime by not voting either Labour or Tory, they were more likely to do so again and it has become much harder to win them back, even at a general election.
In addition, some people have started to vote for different parties at different elections. In Wales, for example, significant numbers have voted Labour in a general election, Plaid for the Welsh Assembly and Lib Dem or independent for their local councillor. People have started to mix and match, enjoying greater choice and liking the idea of politicians having to work together in power.
As the political scientist John Curtice has persuasively argued, "the hung parliament brought about by the 2010 election was no accident. It was a consequence of long-term changes in the pattern of party support that mean it is now persistently more difficult for either Labour or the Conservatives to win an overall majority."
Coalition politics may become a semi-permanent fixture at Westminster, just as it has in local government. In which case, coalition needs to be done a lot better than under the Cameron-Clegg government, where it has become a byword for broken promises, betrayals and sheer incompetence.
By joining with the Conservatives on an agenda that repudiated all their long claims to progressive credentials, the Liberal Democrats lost, if not forever, then for at least a generation, their niche as the ‘anti-politics’ party – the reservoir for the growing group of disaffected British voters.
But, the recovery by Labour of its natural supporters apart, there is no reason to suppose that the two main parties will bounce back to their previous hegemony. Some of the anti-politics vote the Lib Dems attracted has gone elsewhere, especially to UKIP and the Greens. Given the crisis in Europe and the fault line in the Tories, UKIP are likely to poll well at the next general election, mainly at the Tories' expense.
All of this means – and Eastleigh confirmed – that David Cameron won't win the next election. Even on a bad day, and doubtless after a relentlessly negative and well-resourced Conservative assault, Labour is well-placed. On a good day, the party could well defy the odds and win outright in 2015. But it is at the very least realistic for Labour to be the largest single party, able to form a government. The question then is: with whom? And the major answer would come if, as also seems likely, the Orange Book Lib Dem leadership – which hijacked the party and took it into bed with the Tories – is repudiated by a membership desperate to restore the tradition embodied by Asquith, Lloyd George, Keynes, Beveridge, Jo Grimond, David Steel, Paddy Ashdown, Charles Kennedy and Ming Campbell.
That assumes, of course, that there are sufficient Lib Dem MPs remaining after a probable battering in 2015. In constituencies where they are well dug-in against the Tories, such as Eastleigh, the Lib Dems will hold their own, although they will certainly lose seats to Labour.
On the same night as Eastleigh, most pundits missed Labour's spectacular victory in a council by-election in a ward where a Tory councillor resigned. It was in the Tory-held seat of Wirral West, a key marginal which Labour lost last time.
Although he still has ground to make up, the new context for British politics means Ed Miliband is looking increasingly like the Prime Minister-designate.
Peter Hain is MP for Neath and a former Labour cabinet minister. His memoirs Outside In are published by Biteback