When Nigel Farage's dream fades, it will be Dave who smiles

I don't want to disrupt the Prime Minister's tactic of being ever so respectful of UK Independence Party voters, and he was factually incorrect, I think, to suggest seven years ago that Ukip members were "mostly" closet racists, but last week's Ukip surge will matter little at the next general election.

The party is not over yet, and Ukip will do well in next year's European Parliament elections. It will come second. Again. After the 2009 European elections and the Eastleigh and South Shields by-elections, it ought to be called the Runner-Up Party. Labour will come first in the European Parliament elections next year, as the main opposition nationally, and the Conservatives will come third. The Liberal Democrats won't do well at all, but it is that ghastly closed-list proportional system, so they will keep a handful of MEPs. Thus, like the Irish home rulers long ago, the Runner-Uppers will again send more than a dozen old-fashioned men to a parliament in which they do not believe their voters should be represented.

Then, however, it will be time to put away clownish things and to pay attention to the choice at the general election in 2015. During the year before the election, it will get through to many people tempted to vote Ukip that the choice of prime minister is a choice between David Cameron and Ed Miliband. Support for Ukip will fall. An opinion poll carried out by Lord Ashcroft in November found that nearly half of possible Ukip voters would be put off if "my voting for Ukip would make it more likely that the big party I like least would end up in government". Given that the same poll found that Ukip "considerers" prefer Cameron to Miliband by a ratio of two to one, that fall will benefit the Tories. "A Vote for Ukip is a vote for Ed Miliband" is a "pretty simple message", one Downing Street official tells me.

At the general election, scores of Ukip candidates may well save their deposits (gaining more than 5 per cent of the vote), meeting the need for a protest party now that the Lib Dems have gone on to more difficult things, but none of them is likely to be elected as an MP.

The great realignment of British politics will fail to materialise, again. Nigel Farage will wake from his dream of coming from nowhere to replace the Tory party, and the Ukip effect will be reduced to taking away a few of the Tories' less knowledgeable supporters. For those of us who thought that allowing the voters to rank candidates in order of preference was a sensible reform, there is piquant justice in the Ukip voters' second preferences going to waste. But it is not going to make as big a difference as many Tory MPs in marginal seats fear.

It may seem perverse, but David Cameron's party did well last week. It was the worst Conservative showing in local elections since – well, since the party was last in government. The Tories lost a lot of seats on county councils, but those seats were last contested four years ago, when Cameron was a fresh and popular leader of the opposition and Gordon Brown was experimenting with new ways of alienating voters.

The important thing is that Labour did not do as well as it should have done. The party is on average eight points ahead in the opinion polls, which would be enough to win a majority of 90 seats. But when it came to it, last week's elections suggested that Labour is doing less well than that. It is hard to use local elections as a measuring stick for general elections: people vote for different reasons and in only some parts of the country. On Thursday, no one voted in London or in most of the other big English cities, or in Scotland.

Yet it is worth making the effort to glean what we can from the local elections. We can extrapolate from the places that voted to the ones that didn't, because changes in voting tend to be uniform across Great Britain. What matters is how much the Conservative and Labour shares of the vote changed, and what this means for the one number that will decide the next general election: the percentage-point difference between theTories and Labour.

The experts came up with different calculations. John Curtice for the BBC put Labour four points ahead of the Tories; Colin Rallings and Michael Thrasher for Sky News put the gap even smaller. Either way, Labour did worse than its average opinion-poll lead of eight points would suggest. My simple rule is that Labour needs to be only one point ahead to win a majority in the Commons. On Thursday's showing, they are barely over the line.

It may be that opinion polls are a better indicator of how people would vote in a general election, but local elections give a clue, to put it no more strongly, to what might happen when people cast actual votes.

Neither the polls nor the local elections tell us what might change over the next two years, but last week did remind us of one thing that will help Cameron: when the Ukip surge falls back, it will fall back to the Tories' advantage.

However you measure it, Ed Miliband is not far enough ahead to be confident of a majority on 7 May 2015.

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