Bruce Anderson: Mr Cameron had a bad week, and now he turns to face a reinvigorated Chancellor

It was not a good week for the Tories. Liam Fox was unconvincing against Des Browne: hard to get more unconvincing than that. George Osborne made sharp points against Gordon Brown, and asked bothersome questions. The Chancellor blustered the questions aside and was impervious to the points. It was a triumph of rhetoric over reality; nothing that the Chancellor said will restore a single pension or prevent a single mortgage-rate rise. But it rallied Labour's troops and brought David Miliband's vestigial leadership campaign to an end. At the same time, Greg Dyke's vestigial campaign to be Mayor of London was also dying.

In the mid-1980s, Margaret Thatcher's government abolished the Greater London Council. At the time, there were protests. Within a couple of years, no one could remember what the GLC had done, apart from wasting money. But the Labour Party never accepted the decision. It had never objected to wasting money. By the time Tony Blair became Prime Minister, Labour's plans to restore the GLC had been modified. Instead, there was to be a referendum on an elected mayor. This carried, partly because the anti-mayor case was not well-made. A lot of Londoners thought that as other major cities had mayors, they ought to follow suit.

There was one problem. Mrs Thatcher had been insufficiently thorough. She had abolished the GLC, but not Ken Livingstone. The London mayoral race was a contest ideally designed to enable him to embarrass the serious politicians. He started with Labour. In 1997, much of the Labour party still hated Mr Livingstone. Northern and Scottish Labour MPs would have vigorous disputes about him, disagreeing as to how much torture he should receive before being put to death.

So Labour tried to stop him, but ran into an obstacle. The best alternative candidate they could find was Frank Dobson. Who? Precisely. It was no good choosing a dunderhead to run against a jackanapes. The jackanapes will always seem more fun.

Mr Livingstone's victory ought to have been an awkward quarter of an hour for Mr Blair. In those early days, however, nothing could embarass the people's Tony. His political collar remained unfelt. Once Ken had won, he was welcomed back by Labour. Electability was all.

The embarrassment has now moved on to David Cameron. The London mayoralty created a problem for the Tories. They had no obvious strong candidate. They are not alone in this. The British political system is no longer accustomed to producing formidable local politicians such as Joseph Chamberlain or Herbert Morrison, who could move effortlessly from City Hall to the Country Hall at Westminster. While it would be absurd to compare Mr Livingstone with either, his mixture of populism and effrontery allows him to masquerade as a serious politician, especially at a time when many voters are sceptical about politics. But if Ken Livingstone were to stand down, Labour would not easily replace him.

Mr Cameron has been trying to find a strong counter to Ken. It has not been a simple task. A delightful fellow called Nicholas Boles would like to run, but there would be difficulties. Mr Boles is erudite, witty and thoughtful. He has platform presence; it helps that he is about seven feet tall. But no one could claim that he is a street-fighter. If he stood against Ken Livingstone, there would be an irony. Mr Boles is homosexual. It sometimes seems that every third word Ken utters is "gaa-ee", as he fawns on the tendency. Though it would be amusing if one such were to defeat him, I suspect that Ken would merely push Nick Boles down the stairs. In losing, Mr Boles would brand his party as metrosexual, and ineffectual.

Enter Greg Dyke, who is neither. Tories who are disturbed by the courting of Mr Dyke should remember that there are precedents. In 1974, Reg Prentice was a left-wing Secretary of State for Education. As such, he was much disliked by many Tories. Three years later, he crossed the floor and joined Margaret Thatcher. He went on to serve in her government.

At the time, some Tories were unhappy about Mr Prentice. I remember it well, because I had to draft the reply which Mrs Thatcher's office sent to their angry letters. I argued that although tribal allegiance was a bedrock of Toryism, that was not enough to sustain a party of government. As our electoral appeal grew, we should hope and expect to make converts, some of them improbable ones. "More rejoicing in heaven over the one lost sheep" et al. History does not relate whether the recipients were appeased, but Mrs Thatcher had an easier time. Reg Prentice did defect, completely. Moreover, like almost everyone else whose political allegiance alters, he did not just move from the edge of one field to the edge of another. The momentum of change carried him well into the via media of Toryism.

Greg Dyke is a different case. Though his political identity has been destabilised, there is no evidence that he has moved significantly to the right. He is said to retain class resentments. That might seem absurd in a man who has made a lot of money during a successful career, but in England, class feelings have always had little relationship with rationality.

David Cameron decided to ignore all the obvious worries, and press ahead, for one overriding reason. He was convinced that Greg Dyke would be a vastly better mayor than Ken Livingstone. Even if he was not a Tory, there would be much less waste and no further attempts to run a mayoral foreign policy. If the Dyke plan had worked, Mr Cameron would have claimed that he had put London first. As it is, Menzies Campbell saw a chance to embarrass the Tory leader and irritate his natural supporters.

David Cameron has broken the rules. Most political leaders begin by consolidating their base support. Only then do they move out to marginal voters and the centre ground. Mr Cameron has shown himself willing to challenge and bewilder his base supporters, which is why his successes in the centre ground have not yet given him a larger lead in the polls.

We will know a lot more in two weeks' time. If the Tory results in England can be extrapolated to 45 per cent at a general election, Mr Cameron is entitled to drink some seriously good champagne. Even at 42 per cent, there are grounds for cautious celebration. A near 40 per cent would only justify small beer and a rapid return to work.

Gordon Brown cannot wait to lock horns with his Tory challenger. He is convinced that he can rapidly assert mastery. There are plenty of reasons to question this, not least the inflation rate. But we can be certain of one thing. Anyone who takes on Gordon Brown will know that they have been in a fight. In such circumstances, it always helps to make sure that your own supporters are solid.

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