Ukip has a sell-by date... and it's May 2015

The by-election last week was a disaster for the UK Independence Party. The party rode a wave of hostility to politics and of hostility to the European Union, and now the two waves are subsiding. I doubt now that Ukip will ever establish itself as a serious force. There simply isn't the time before the general election, and after the election everything will be different. It will be like the effect of climate change: Ukip will be driven to extinction by the destruction of its habitat.

I say this as someone who welcomes Ukip's contribution to our ecology. I do not oppose in principle the party's central policy. On balance I think that Britain should remain in the EU, but only just about, on balance. I do not think that it is xenophobic or fruitcake to assert that there would be advantages in being outside it, especially while most of it is locked into a flawed currency union. But I think Ukip is probably finished.

The by-election in Wythenshawe and Sale East was the party's penultimate chance to shift things into a new pattern. It was a big chance to protest against politics as usual, to allow voters to express their rage against the three main parties. All three parties are, incidentally, committed to British membership of the EU, but this was supposed to be a bigger protest than that: a warning to all the Westminster parties that the voters had had enough, of their being "all the same", "in it for themselves" and "breaking promises".

Ukip was supposed to have replaced the Liberal Democrats, for decades the recipient of the protest vote but currently unavailable for that constitutional duty owing to the pressing need to get in and out of ministerial cars, on and off ministerial bicycles, and make ministerial decisions, such as classifying ketamine as a class-B drug rather than C.

Starting in 1962, the Liberals and Lib Dems have won sensational by-elections and built themselves up as the alternative to politics as usual. That was what was supposed to happen for Ukip in Wythenshawe, but it didn't work out like that. What happened was that "politics as usual" reasserted itself. A well-organised Labour campaign – there were 13,000 postal votes, nearly half the turnout – managed to channel anti-politics sentiment into an anti-Government vote, a 55 per cent vote for Her Majesty's Official Opposition.

Ukip now has an unparalleled record for coming second. Second in the Eastleigh by-election – beaten by the eclipsed Lib Dems, who show an extraordinary ability to hold on to what they have and lose their deposits everywhere else. Second in South Shields, a Labour seat that was supposed to be the practice run for the Wythenshawe breakthrough. And now, in light of a miserable 18 per cent share of the vote in Wythenshawe – miserable, that is, by protest-vote by-election standards – second in their share of the vote in the coming European Parliament elections in May too.

It looks highly likely that Labour will win the most votes in those elections. Our ComRes poll today has Labour overtaking Ukip in its "favourability" rating, and even Ed Miliband overtaking Nigel Farage. Ukip may win more votes than the Conservatives, but "beating the Tories into third place" lacks the shock value required to overturn the accepted order.

So, that is it. That is the end of the Ukip insurgency. Farage himself might win one seat at the general election next year, as a national celebrity in a well-chosen target seat. Thus Ukip may end as more successful than the Green Party, whose Caroline Lucas will probably lose its one seat next year, but less successful than the Social Democratic Party, which once had 30 MPs by defection and eight by election, before merging with the Liberals.

It remains to be seen how Ukip will affect the Conservative vote in the general election, but the point to remember about that is this: to the extent that Ukip syphons off Tory support, that is already reflected in the opinion polls. Labour has a five-point lead in our poll today after Ukip has stolen Tory votes. If Tories hold their nerve, Ukip is unlikely to take more votes from them between now and the election. All that matters is whether the booming economy – Mark Carney, the Bank of England Governor, last week predicted growth of 3.4 per cent this year – is enough to swing that five-point Labour lead into a four-point Tory one, which is what David Cameron needs to stay on.

Whoever wins the election, Ukip's habitat will change. If Cameron wins, he will hold a referendum on Britain's membership of the EU. Ukip would be prominent in the "No" campaign, but after the referendum – even if it's a No victory, which seems unlikely – the party would no longer have a purpose. If Ed Miliband wins the election, a referendum is not so certain, but a Conservative Party in opposition would be freed from the constraint of office and might become so anti-EU that Ukip would, again, become unnecessary.

That is the thing about "politics as usual": one of the things it usually does is adapt and absorb eruptions of popular sentiment without breaking.

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