John Rentoul: Brown's bungee jump is nearly over

The Prime Minister's ups and downs will eventually come to a stop, but he probably has one more high left in him

Gordon Brown has one bounce left. At some point in the next few weeks or months, there will come a respite. As the Prime Minister said in the House of Commons when Patrick Cormack (Conservative, Light Relief Central) asked what he wanted for Christmas: "I want to I might have one day off."

There will be a break in the clouds. The days will get longer again. There are deep rhythms in politics. Remember August and September it wasn't that long ago but seems like a different era after David Cameron went to Rwanda? There were serious rumblings about Cameron's leadership as Labour seemed to have settled into a solid opinion-poll lead.

It turned out, though, that that was the "Brown Bounce": an extended lifting of the spirit after the claustrophobia of the last days of Blair. It peaked in a batch of four consecutive polls that gave Labour double-digit leads after Brown's Bournemouth conference speech. That was, as some people said at the time, the best that things were going to get.

Since then, it has been a juddering downward ride. Brown has been unlucky, and his decline has been unfair. He cannot be blamed for most of the disasters that have knocked him back, and some of them haven't even been disasters. Despite the Cult of Cable that seems to have gripped the political classes, the acting leader of the Liberal Democrats has been quite wrong, for example, to suggest that any course of action other than guaranteeing Northern Rock deposits was sensible.

The only presentational mis-hit that was definitely Brown's fault was the dithering over an early election, which came at the start of, and set the tone for, the whole ghastly sequence. But, really, how serious was that mistake in reality, rather than in perception? How many people's life chances were adversely affected by it?

Of course, there is much about which to be disappointed with Brown. At his news conference last week when a foreign journalist asked him for a progress report on his "vision", he gave a formulaic answer about affordable housing, raising the education leaving age and reviewing the health service. I don't agree with any of those, but only on education do the Conservatives offer the beginnings of a credible alternative.

Yet Brown's standing in the eyes of most voters has gone down because junior civil servants, statisticians and party functionaries have made the sort of mistakes that could occur under any government. Admittedly, the cracks from the latest disaster are spreading close to Brown's feet. He made a mistake in backing Harriet Harman over Alan Johnson for the deputy leadership. Cool-hand Johnson would be an asset as his number two now. And Jon Mendelsohn, who was appointed by Brown to raise clean money for Labour, has had to resort to the "have you tidied your room" excuse: "I was just going to."

Most of the bad headlines of the past 10 weeks have been emphatically not Brown's fault. Still, it will not go on for ever. There will be a "Second Bounce". Cameron will make a mistake, or some Tory councillor, tiring of the trammels of politics, will say something outrageous. One staffer at Tory HQ has even put an expected frequency on such "unhelpful" contributions, pencilling them into the grid at six-weekly intervals.

For Brown, unhelpful stories have disrupted his media planning grid at roughly six-hourly intervals of late, but the laws of probability dictate that he must have a little more than "one day off" some time. Journalists will also become sated with the "Brown Down, Cameron Up" story, and will want to sample the flavours in the opposite combination again.

Curiously, The Second Bounce of the Ball: Turning Risk into Opportunity is the title of a book just published by Sir Ronald Cohen, Brown's favourite financier. (At least he hasn't got him into trouble.) It is something to do with the unpredictability of where a ball will bounce next. I am sure it is a brilliant guide for entrepreneurs but it does not help much with politics. I do not see Brown turning his present risk into much of an opportunity for long.

The next up phase is likely to be what they call in the City a dead-cat bounce. Brown can be a new prime minister only once. If he bounces back, he is unlikely to rise as high as in the summer. After that, I think it is over.

The mood in the country has gone against him. As one Labour MP said to me the other day: "People want Tony back: it takes the form of being prepared to vote for Cameron." A BPIX poll last weekend found that more people said they would vote Labour if Tony Blair were still prime minister. L A Lawrence of Devizes wrote to the editor of The Daily Telegraph: "Sir, Having spent 10 years berating Tony Blair, I now wish to form a Blair Appreciation Society for protecting us for so long from Gordon Brown."

As I say, it is unfair, a lot of it for superficial and irrelevant reasons, but the chances must be against Brown's being able to pull it back. Jack Straw betrayed the desperation of the inner sanctum last weekend when he said: "We're two and a half years away from a general election." That sounds like two and a half years of Brown becoming more unpopular and Labour heading to more certain defeat.

This time next year, therefore, after Brown's second bounce has dribbled away, the party is likely to turn to David Miliband. Fittingly, he foretold Brown's woes. Nine months ago he said on BBC1's Question Time: "I predict that when I come back on this programme in six months' time or a year, people will be saying, 'Wouldn't it be great to have that Blair back because we can't stand that Gordon Brown.'" He meant that to lead is to offend, but unconsciously hit on the dynamic that would propel him upwards.

The wisdom of the wise is that Miliband is not ready, or that he never will be ready. And it is true that, as Foreign Secretary, he has lost some of the fluency, urgency and thoughtfulness he showed at Environment. But he has the youth, the green credentials, the charm and the brain power to trump Cameron.

If the voters have already decided that Brown is not right for the job and that they want someone more like Blair, then Miliband is the only Labour rival to Cameron that could rise to that call. Straw is doing well as the "ambulance" candidate, should anything happen to Brown in the short run although I notice that supporters of Johnson pressed his claims to that role last week. Johnson's problem is that he said on Desert Island Discs in October of the job of prime minister: "I don't think I've got the capabilities."

David Miliband does have the capabilities. The question is whether he has the ambition. I understand that Blair, who wanted him to challenge Brown in June, has his doubts. I think that is a misreading: Miliband refused to run because he didn't think he could win. Then, he was right.

Give him a year and not only will he be ready, but the country will also be ready for him.