In the end, will a blur replace a Blair?

Four years ago the late Robin Cook offered to bet me a tenner that Gordon Brown would never become prime minister. And I cannot but wonder whether he would have been prepared to say the same thing today.

The polls are bringing not merely grim tidings for Labour but potentially devastating news for the chancellor of the exchequer. They are playing on his darkest fear - that the prize he has ached to get hold of for so long will be snatched from him for a second time.

By informing the nation that Labour would do little if at all better electorally under his leadership than currently under Tony Blair, opinion polls are inviting many people in his party to ask themselves some tough questions: “Can we win with Gordon? If not, why elect him? Is there anyone we could sensibly elect instead?”

It is in such a strained atmosphere that education secretary Alan Johnson has suddenly found himself being catapulted by some political observers into the positions of the man to stop Gordon, and the next Labour leader and prime minister.

The speculation mill at Westminster went into overdrive last week after he had openly expressed interest in becoming deputy leader of his party when there is a vacancy.

“I want John Prescott to stay as deputy leader for as long as he wants to be deputy leader. So there's no campaigning going. But people have asked me if, when there is a vacancy, I'd be interested in that vacancy and I've said quite honestly: yes, I would,” he declared in a GMTV studio.

What a refreshingly candid answer, you might suppose. What a pity, you might think, that so many politicians - Mr Brown, for example - seem almost congenitally incapable of talking in such straight terms. But Mr Johnson should have realised - if he didn't - that his words could be interpreted as those of a deeply ambitious man keen quickly to replace Mr Prescott. Why didn't he dodge the issue? The fact that he didn't proved to some minds that he couldn't wait to return to Dorneywood (as in Mr Prescott and croquet) where he used to deliver letters when working as a postman.

It didn't stop there. Just a few days later he was being portrayed by some not just as the next DPM but the next PM. It is possible this was largely tongue-in-cheek and mischievous.

But a reasonable case can be made for Mr Johnson. It includes the facts that he has risen to cabinet office from humble origins, that he has done so without (so far) creating enemies, that he performed skilfully when he was Charles Clarke's right-hand man in getting student top-up fees through the Commons, that he has good trade union contacts (having been general secretary of the Union of Communication Workers), and that (unlike Mr Brown) he is both English and plainly a fully paid-up member of the human race.

Put against Mr Brown's heavyweight CV, however, his does look rather modest. He is a little open to the gibe of having risen virtually without trace. And what does he actually stand for? Is he an out-and-out Blairite? Does he believe in permanent revolution in the running of the public services? Or does he represent a particularly bland form of Blairism with Old Labour edges?

Virtually every elector must know by now what he/she thinks of Mr Brown. The picture in the mind might typically generate only grudging respect and little affection, but it should at least be pretty clear. By comparison, Mr Johnson is a blur if not almost a complete unknown.

That can be overcome. A year ago only a tiny proportion of the population had heard of David Cameron. But it is not at all clear that Mr Johnson even wants to become Labour's leader, and there is a very big obstacle in his way. Mr Brown is devoted to getting the job, and is intent on crushing anyone who seriously gets in his way. If Mr Johnson really does fancy having a go, he had better watch out. It will be no surprise if several derogatory comments about his abilities are soon doing the rounds at Westminster and in the media. A conclusion may already have been reached in Brown circles that he is getting above himself and needs to be taught a lesson.

The key element in the conjecture about Mr Johnson is the strength of the longing for a good alternative to Mr Brown as Mr Blair's successor. If it's not the education secretary, who is the 'Stop Brown!' figure who can also stop Mr Cameron? It might not be any more obvious in a year's time that such a person actually exists. But the temptation for Mr Blair to stay on at least that long to find out is easily understood.