John Rentoul: Beware 'The Boris Effect' - it could mean nothing at all

Johnson's victory is neither a criticism of the Prime Minister nor a threat

Labour did well at the polls last week, apart from in the London mayoral contest. But Boris Johnson's win is a headache for David Cameron, because Boris wants his job. The UK Independence Party did well, threatening to stop the Conservatives winning a majority at the general election. And the defeat of all but one of the referendums on directly elected mayors is a crushing setback for the Prime Minister and his big idea of localism.

All these early wisdoms about last week's voting are mistaken. In the local council elections, Labour secured 38 per cent of the national vote, according to the BBC's projection, to the Tories' 31 per cent. Respectable, but a seven-point lead two years into a parliament is nothing special. It is even less special because we have a coalition government.

If we add the 16 per cent of votes cast for the Liberal Democrats, a total of 47 per cent voted for the government parties. This may seem a curious way of looking at it, because the most important number at the general election will be the difference in votes between Labour and the Tories. That is what will decide whether or not either party has a majority or how far short of a majority they fall.

However, it is easy to overlook the difference a coalition makes, just because two-party government is so unfamiliar. Mid-term elections are chances to protest, and it isn't much of a protest against the Government to vote Liberal Democrat. That is why it is hard to claim, as Ed Miliband did, that these elections are a "wake-up call" to the PM, or a forceful demand for the Government to change course.

Labour is right, though, that Boris Johnson's election proves little about the Tories' chances at the general election. He defied the national trends because he is a great character. Labour people were quick to blame Ken Livingstone for his own defeat, although he is a great character too, and I think Boris would also have beaten Oona King, who was Ken's main rival for the Labour nomination. But Boris's victory is neither a criticism of Cameron nor much of a threat to him.

Even before the votes were counted, Boris's win was hailed by Tory rightwingers as a vindication of their complaints about the PM. Tim Montgomerie, editor of the ConservativeHome website and the leader of the party's internal opposition, wrote in The Times on Friday that Boris "is the one senior Conservative who simultaneously appeals to core Tory voters and to a large proportion of Labour supporters" and, if Cameron did not respond, "the party might very reluctantly reach for the blond-coloured nuclear button".

This makes no sense. Some "core Tory voters" – not many – might applaud Boris's defence of bankers, but it is not an obvious way to appeal to Labour supporters. Nor is his support for immigration an obvious way to secure his right-wing base. He appeals to all kinds of people much less because of ideology and much more because he is an engaging personality. Or buffoon, according to taste.

The same principle applies to Ukip. The Tory right have the argument the wrong way round. They argue that Ukip will take "right-wing" votes from the Conservative Party unless Cameron is ruder to other European leaders and promises tax cuts. That is not how politics works. Ukip is a protest vote if the Tory party is unpopular: the ideology is secondary. If Cameron is seen as a strong and competent leader, regardless of his policies, Ukip will lose support.

That leaves the option, for the Tory party, of drafting in a more popular leader if it decides Cameron is so useless that he is going to lose the next election. It may be that the Murdoch business, or some other scandal, could bring him down. But even if that happened, Boris is an unlikely successor.

In the 19th and early 20th centuries, politicians were found seats in the Commons almost by invitation. It is not so easy now, and Boris is chained to City Hall until after the general election. And that is without even considering whether he, entertaining as he might be as mayor of a greatcity, is the right person to put in charge of a nation's nuclear deterrent.

As for the defeat of directly elected mayors, everywhere except Bristol (and Doncaster), the idea that this reluctance to switch from one kind of local democracy to another is a setback for the PM is, I'm afraid, a journalistic fiction. Locally, it might make a difference – Bradford will not have a Respect Party mayor, for example. For Cameron's prospects, it does not matter a bean.

Still, hailing false dawns is what the Labour Party in opposition has always been good at, and there is another one breaking tonight. The likely election of François Hollande as president of France will prompt a lot of guff about the revival of European social democracy, when it would mean no such thing. The left was swept out of government across Europe because its high spending was unfairly seen as contributing to the fiscal crisis; now the right is unpopular because it is responsible for austerity.

It is possible that Ed Miliband could benefit at the next election from a similar revolt here, but last week's elections were not evidence that Cameron is doing badly enough yet for that to happen.;