John Rentoul: George laid a trap for Gordon, he snared Dave

It was a scene from Laurel and Hardy. George Osborne, the shadow Chancellor, digs a trap for Gordon Brown. He covers it with branches and leaves. Brown walks straight past it. Along comes David Cameron and falls in.

Osborne's speech on Wednesday was more explicit than before on the Conservatives' promise to continue the popular bits of Blairism. Osborne's pitch was that the Conservatives and Tony Blair are part of a forward-looking "consensus" for reform, while Brown wants to go back. Just as Blair once built a coalition that included Liberal Democrats and moderate Tories, making the Tory leadership seem extreme, so Cameron wants to draw in Liberal Democrats and Blairites. He seems to expect Brown to fall into the trap of agreeing that "choice", as Osborne put it, is a "bad word in the Labour Party again".

This fits the pattern of Cameron's leadership. It is (a) a mirror copy of New Labour; (b) broadly right; and (c) badly executed. Cameron and Osborne have identified Brown's difficulty accurately. He has a big problem reassuring Labour's core vote, especially public sector workers, while at the same time holding on to the non-core vote that came to Labour for the first time in 1997.

Brown is trying to pull off this trick by using a proxy. He has been gently in favour of Harriet Harman's campaign for the deputy leadership while hedging his bets with other possible winners. Six identifiable Brownite MPs nominated her, while Treasury ministers Ed Balls and John Healey acted as Brown's side bets on Alan Johnson and Hilary Benn respectively.

Harman appears to have been licensed to be the respectable face of Old Labour, wanting higher taxes on "fat cats" in the City and saying that the Iraq war was a mistake. She has a history with Brown the ventriloquist: as a Cabinet minister addressing the 1997 Labour conference, "unfamiliar words started coming up on the autocue" - and she realised the Chancellor had rewritten her speech and not told her.

Meanwhile, Brown has attracted media attention not for being different from Tony Blair but for being the same. He refused to rule out military action against Iran and suddenly developed an interest in academies - even going so far as to visit one. This was significant because it was the attempt by David Willetts, Tory education spokesman, to trap Brown on academies that led the Tory leadership into the quagmire of grammar schools. In the course of trying to be more pro-academies than the Chancellor, Willetts said they, rather than grammar schools, were the way to deliver social mobility.

Brown is vulnerable - anyone who has to rely on Harman to deliver a balancing message is not in a strong position. She wanted to be deputy leader to Blair in 1994, but he would not have her. When Philip Gould, his pollster, told Blair that she came across well in the research, he was told to "go away and refocus your focus groups".

However, the Conservative row over academic selection, now in its 18th day, has distracted everyone from Willetts's original purpose. The Tories thought academies were a wedge issue that could separate Blairites from Brown, because they offer parents the choice of new schools in the state sector. What they desperately want is a big Blairite catch: they want someone credible to come out and say that they supported Blair's plans for public service reform, but now think Cameron is the right leader to deliver them.

For all the speculation, over the past year, that some of Blair's closest associates preferred Cameron to Brown, no such defector has appeared on Glienecke Bridge. But wait: is that Julian Le Grand lurking in the mist, ready to come over? The ideologist of choice in public services who was Blair's health policy adviser said last week: "If David Willetts becomes Education Secretary, if they do get into power, that would be a good thing." But it was a trick of the light; he added: "It won't change my vote."

Last week's confusion over Tory policy on grammar schools was not good for Cameron, but it was a ring-fenced retreat. Although new grammar schools would be permitted, as they are now, in growing towns that already have selection, Willetts said an unambiguous "No" to selective state schools elsewhere. The grammar school row will rumble on in the Conservative Party, but it has nowhere to go.

But that was not the worst trap into which Cameron fell last week. More serious than a technical footnote to a copy of the Government's schools policy that has failed to split New Labour was the decision to appoint Andy Coulson as the Tory director of communications.

Coulson is an able man. People whose opinions I respect speak highly of him. But his appointment breaks the first law of spin-doctoring before he starts work. The first law is that a press officer ceases to be effective when he or she becomes the story. That was why, in the end, Jo Moore and Alastair Campbell had to go. Indeed, one of the smaller mysteries of the Blair years, for which we look to Campbell's edited diaries next month for the answer, is why Moore was kept on for so long after describing 9/11 as "a very good day to get out anything we want to bury".

Coulson comes to the job as a story - and it is not the one-day wonder of Cameron hiring his own Alastair Campbell. Coulson was editor of the News of the World when its reporter was jailed for hacking into royal voicemails. Whether or not he knew about it, it happened "on my watch", as he said in his resignation statement, and it was one of the least edifying episodes in recent press history.

More than that, though, he was editor of the News of the World. This seems to be upsetting Tory MPs even more. What signal is sent by hiring the man who sold salacious celebs'n'sex journalism, whose main experience of politics was to be the conduit by which David Blunkett's affair with Kimberly Quinn became public? People may find Brown's Presbyterian seriousness a little daunting, but this may be going a little far towards the cult of celebrity that the next Prime Minister decries.

If Cameron thought he needed a figure like Alastair Campbell, he was right again in his analysis, but wrong in his execution. To compare Coulson to Campbell is a category error. The point about Campbell is that he lived and breathed politics. He fitted perfectly into a New Labour machine that fused policy-making and message discipline into what Philip Gould, another cog in the machine, called "a unitary command structure".

Equally, if Cameron hopes that Coulson will deliver Rupert Murdoch's media empire, it will only look like a murky backroom stitch-up if it works.

Cameron looks as if he is trying to copy New Labour - which is the right thing to do strategically - but is just making a horrible mess of it. As the Conservative leader says today about his attempts to go green in his personal life: "You'll find lots of holes." They are beginning to show.

Further reading: 'Cameron: The Rise of the New Conservative', by Francis Elliott and James Hanning; George Osborne's speech http://tinyurl.com/35labg

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