Labour is disappearing up its own fundamentals. The depth of self-obsession of the leadership non-contest would be hilarious were it not so serious. Take the idea, floated yesterday, for instance, that were David Miliband to declare his backing for Gordon Brown, he could be offered a “key” post in the Chancellor’s campaign team; deputy chairman to campaign manager Jack Straw, perhaps.

Now how key is that? Deputy to a man running a campaign to stop there being any campaign . . . In a contest that no one cares about because it doesn’t exist. The way things are going, the change in the Labour leadership is going to enervate politics, not enthuse it.

Look at the widespread interpretation of Mr Straw’s appointment as a “coup” for the Brown campaign. Only in a sort of fantasy Westminster politics it is. Mr Straw, as is obvious to anyone with half an eye on politics rather than a living in it, is simply interested in a plum position in the subsequent Brown Government. Securing Mr Straw’s agreement to be campaign manager must have been about as hard as securing a donkey’s agreement to spend a day in a carrot shop.

If that is clear to the average observer, who will see an admirable enough but ageing politician assuring himself a few more years in the featherbed, so too will be any proclamations of support from ambitious younger ministers such as Liam Byrne and Andy Burnham. I would go so far as to suggest that most normal people (ie, outside SW1) will look at the early protestations of support gathered up by the Brown camp and presented like offerings to the gods and think (a) of course they have to say that; (b) why is the Chancellor so insecure that he needs to arm twist all these people now? (c) this is a stitch-up.

And (c) is important, because they are thinking not that this is a stitch-up for the leadership of the Labour Party, but this is a stitch up for the leadership of the United Kingdom, and to the electorate, that rightly matters rather a lot.

There is another thought creeping into people’s minds: what is the Chancellor so afraid of? If he doesn’t have the self-belief to think that he could win a contest for the Labour leadership, if he is nervous of revealing more of his programme in open debate with colleagues, then why should we want him as prime minister?

An event that ought to be a showcase for intellectual confidence and inspiring debate, evidence of Labour’s future, looks from the outside like a strong-arm stitch-up by a self-interested old guard whom all the youngsters are too afraid to cross. It is a most unattractive impression.

And it is so unnecessary. For it is precisely because this is an election for prime minister, not just party leader, that it would in fact be extremely difficult for any other candidate to beat Mr Brown in a proper contest. The young and untested David (Cameron) might have been an attractive proposition to the public as leader of the Opposition; the young and untested David (Miliband) is likely to prove less so as leader of the country. Or maybe not. I don’t know — no one does — but I sure as hell would like to find out.

The Budget was a disaster for Mr Brown. He ditched his principles, attacked the poor and didn’t even get any credit for a 2p tax cut from the voters, who overwhelmingly thought their taxes would be the same or more than before. The postBudget poll in The Times also showed a massive slide in his ratings as a future prime minister since three months ago: from a minus 9 rating to a minus 27. (Tony Blair’s ratings are on the up, by the way.)

The reason he failed to win round the voters is simple: he wasn’t straight enough. The Budget was a masterful example of Brownite trickery; all illusion and political cleverness adding up to, for most people, precisely nothing. And people saw through it. They tend to, now: when they see a Brown party trick, they look for the smoke and mirrors, not the rabbit.

The Times/Populus poll today on the Scottish elections is terrible for Mr Brown as well: ten points behind on his home turf. Yes, Scotland is different; yes, the SNP is a more attractive protest vote to disillusioned Labour supporters than are the Tories in England; yes, the fight up north is not over yet. But still.

You can’t just keep a lid on these doubts. You have to answer them. And the best way to answer them is to have an open, broad leadership contest that showcases the best that Labour has to offer and answers the doubts of the electorate.

Something has to change if this noncontest is not to prove a knockout blow for Labour. At the moment none of the potential Labour candidates is looking very attractive. A leader needs the courage of his convictions, and neither Mr Miliband nor Mr Brown is showing much. It looks like cowardice all round and who wants a coward in charge of the UK?

Mr Brown needs to show, as he did not with the Budget, that there is more to him and his campaign than spin, manipulation and underhand tactics, and an open contest could do it. I think he would probably win it, but with his reputation and position — and Labour’s too — enhanced. And if he cannot win it, then he shouldn’t be the next prime minister.

For like it or not, and this is what Labour is in danger of ignoring, this is the public’s election too. This is an election for prime minister. And the only way to give the public a say in it is by allowing them a good hard look at alternative candidates and their ideas, and letting public opinion filter into the contest. Or Labour can continue the way it is going, and the next prime minister may find himself out of No 10 before too long.

Times Recommends

• Tear down this wall! And save the planet
• Double click if you want the bin emptied
• Have you got permission to read this?