John Rentoul: Brown will face a contested election for the leadership

'Luck is where preparation meets opportunity'

Of all that was new about New Labour, green politics were always a bit of an afterthought. The Government was caught off balance by the petrol tax revolt of 2000, and has struggled since. To his credit, Tony Blair has been good recently at global consciousness-raising about climate change. But when it comes to practical action, Labour has been cautious and defensive, allowing David Cameron to seize the initiative.

All we will get in Manchester this week is meaningless guff about "sustainable communities", and next week Cameron will promise to make hard choices to cut carbon dioxide. He has not said what they are yet, of course, but my guess is that he will beat Gordon Brown to specific "tough" policies.

Green issues are, therefore, surprisingly important to Labour this week. You might have thought that the big question was whether Alan Johnson or John Reid would stand against Brown for the leadership. But the answer to that is simple: one of them will. Let us come back to that in a moment. The next question is: who is best placed to take on the Conservatives? And green stuff is central to the answer. Because the initiative in British politics has passed from Blair, who has held it since 1994, to Cameron. The Blair who addresses delegates this week is already bathed in the numbing narcotic of sympathy. Our opinion poll finds that 55 per cent of voters agree he has been "badly treated" by his party. But you feel sorry only for the powerless. How quickly the caravan moves on.

It is Cameron who is setting the pace, powered by environmentally friendly fuel. Our poll also reveals that people are not as cynical as Labour would like them to be: more agree that Cameron's greenery is a "deeply held conviction" than disagree.

Blair's unscripted session at the TUC was a cusp moment. Asked to reflect on the occasion of his last address, his voice cracked as be pleaded with delegates to realise the "brutal truth" that winning elections was a necessary evil. "I meet people who for the first time have been able to afford a holiday abroad because of the changes we have made," he said.

There, in a sentence, lies the contradiction between the politics of the past and the future, with Blair unusually and emphatically on the side of the past. That air travel is a good thing is no longer a given. Aviation is not the biggest cause of global warming, but it is the fastest-growing, and anyone who is serious about the environment has to work out how to restrain it. Blair has always been dismissive of this country acting alone ("preventing British people getting on planes", he called it) while saying "it is unrealistic to think that you will get some restriction on air travel at an international level".

This is a cusp issue, as our poll confirms; voters are split down the middle over the desirability of more expensive flights. But Cameron is on the right side of a moving wave. As Blair takes his bow, the real business of the Labour conference is to decide how to respond, for the first time in 12 years, to an external threat.

Gordon Brown remains the obvious answer, despite other polls that suggest Labour would fare even worse against Cameron if he took over. Such findings are important, but not predictive. If Labour want someone to pulverise Cameron, Brown has the record. He can attack Cameron as the adviser who lurked in the shadows when Norman Lamont publicly shredded Tory economic credibility, coming out of the Exchange Rate Mechanism. And he, alone among Labour candidates, can compare that loss of Tory credibility, still not recovered, with his own exceptional record as the most successful Chancellor since the invention of paper money.

It is a powerful claim, but it is backward looking - albeit that it uses the past as a guide to the future - and, since this month's attempted coup against Blair raised the character issue, Brown has ceased to carry all before him. He will, therefore, face a contested election for the leadership against either Alan Johnson or John Reid.

This prediction is not based on that most unhelpful of footnotes, "private information". Although a condition of making it is that I am confident that neither Johnson nor Reid has, in the privacy of their own ambitions, ruled out a run at No 10. They have both made clear to friends that there is, in the old New Labour phrase, no cap on their aspirations. They are, therefore, in a different category from David Miliband, the Environment Secretary, who is emphatic in public and in private that he will not be a candidate for leader or for deputy leader. The limits of Miliband's ambitions for the foreseeable future are that he should be education secretary or foreign secretary under Prime Minister Brown.

The question, therefore, is what Johnson or Reid has to lose. The fate of Bryan Gould is usually mentioned at this point. He ran for both leader and deputy in 1992 and was humiliated, 91 per cent to 9, by John Smith. That, though, was under the old Bennite rules, when trade unions and constituency parties voted in blocks. Where ballots were held, Gould averaged one-third of the vote. A YouGov poll of Labour members this month suggested that one-third would vote for someone other than Brown. That would be a respectable showing under the present one member, one vote system, with most of the risk on the up-side. Enough to ensure that the "incredibly inclusive" Brown, as he described himself the other day, would have to include his defeated rival in a top cabinet job.

So the secondary issue is which it will be: Johnson or Reid? Presumably, whoever collects more nominations from Labour MPs will defer and release his MPs to nominate the other, thus reaching the threshold of 45 required. Johnson has the advantage of easy clubability in this quest but Reid seems steelier of purpose. As he said to The Spectator: "Luck is where opportunity meets preparation." He has just taken on Lord Alli, the media entrepreneur, and Baroness McDonagh, Labour's formidable former general secretary, ostensibly to advise him on Home Office reform. That is the preparation: now he needs the opportunity.

Brown's speech tomorrow is the main event. I suspect that it will disappoint without being disastrous. Blair's speech will be a virtuoso performance, but it hardly matters. If you really want to know what is going on this week, listen to what Alan Johnson and John Reid have to say about the environment.