Leading article: Mr Cameron issues his own electoral challenge

David Cameron, it was being said as the party faithful gathered in Blackpool, would have to make the speech of his life if he was to retain his credibility as Conservative leader. In the event, Mr Cameron's serious and at times rambling political tour d'horizon fell some way short of the brilliance that had dazzled delegates two years before. But circumstances had conspired to set Mr Cameron quite a different mission from either the one he had accomplished so conclusively from the same platform in 2005, or the one he had expected to face this week.

By yesterday afternoon, it was less the scepticism of his party that he had to overcome – the threat of an imminent election had tamed the party and potential rivals into grateful quiescence – than the scepticism of the country at large. With speculation about a snap election rampant, Mr Cameron suddenly had to present himself as a plausible Prime Minister and a credible rival to Gordon Brown.

It is fair to say he did everything he had to do, and probably a little more. The doubts he had to dispel in his speech were all to do with competence and personality. He had to demonstrate he had a coherent political purpose and he was more than a silver-tongued PR man from the privilegentsia. His conscious show of spontaneity – no script as such, no autocue, as he pointedly stressed at the outset – was the first of many digs at Gordon Brown.

The tone of sincerity and solidity, the desire not to appear too polished, smacked of a conscious effort to neutralise a key aspect of the Prime Minister's post-Blair appeal. His closing "confession" about his comfortable upbringing, the benefits of an Eton education and the rest was an undisguised strike at Mr Brown's narrative about character, sports injuries, and the values imbibed as a son of the manse. Mr Cameron was wise to admit that his personal story lacked the colour of Mr Brown's. But he was wise, too, to admit his social advantages for the public record.

As striking as Mr Cameron's efforts to confront Mr Brown on the personality issue was the extent to which, in policy terms, the two are contesting the same ground. On the family, education, the NHS, security and immigration, Mr Cameron ploughed a furrow not so very different from Mr Brown's. On immigration, he contrived to sound more broadminded than many a Labour minister. He also stuck to his guns on the need for action on climate change, though with the usual lamentable lack of specifics.

The differences that are emerging between them, however – on taxation, on ID cards, on a referendum on the EU treaty – are, it is increasingly clear, reflective of genuinely divergent world views. One of Mr Cameron's guiding principles is that he wants the state to retreat as far as possible – from local government, and from schools and from the NHS. His concern about social mobility and civil liberties is born of a rather traditional One Nation Conservatism, albeit one to which he gives a modern and green-tinged twist.

Mr Cameron demonstrated yesterday that he may be able to rival Mr Brown on substance as well as style. Whether a couple of eye-catching tax concessions and a confident leader's speech will dent the lead of a Prime Minister with so much experience and gravitas, however, is another matter, especially given the fractious pre-conference mood of the Tories. Perversely, Mr Cameron's strong performance yesterday could make it less likely that he will find himself fighting Gordon Brown very soon for the keys to No 10, while any perception that Mr Brown was now flinching from an election might even the match further. Election or no, we can expect to live in interesting political times.