So rubbish is the new brilliant, is it? Here’s the theory. Yes, Gordon Brown was really boring on Monday. Yes, he had nothing to say, but took 65 minutes to say it. Yes, his statements of belief were astonishingly incoherent. Yes, his stunning strategic move was to pinch the clothes of the Tory party, failing to recall that they were the garments the Tories wore when they lost three elections.

There was remarkable agreement in Bournemouth that the Prime Minister’s speech was poor. Even his most enthusiastic supporters weren’t claiming it was Demosthenes.

But what you have got to understand is that it was all done on purpose. He meant to be dull, you see. The cheesy rhetoric showed that he was too busy running the country to be bothered with crafting good phrases. His shopping list of cheap populist promises was not a worrying revelation that there is nothing there, it was a clever move to dish David Cameron. His lack of a single funny joke was designed to emphasise his seriousness. It was rubbish, but, hey, wasn’t it fantastic?

It’s remarkable how such an eccentric theory has taken hold in the media, but it has. I just keep reminding myself that moods pass. Noel Gallagher’s visit to Downing Street was hailed as a masterstroke, Cool Britannia was regarded as a vote winner and it was believed to be miraculous that Mr Cameron could ride a bicycle.

So I dedicate my column to these two assertions. That rubbish is rubbish is rubbish. And that Gordon Brown can call a snap election if he likes, but he might not win it.

As Mr Brown spoke, I realised I was listening to something vaguely familiar. And then suddenly it came to me. He was repeating the standard Tory platform speech from the 2005 election, right down to the pledge to clean hospital wards.

The pitch was exactly the same. In place of the tricksy Tony Blair, let’s put in a hard man who can get the job done, someone who acts rather than emotes. And with the hard man comes a series of hard pledges all about foreigners and guns and drugs and things. These promises come straight out of focus groups. You make liberal use of the two phrases that get applauded at both party conferences – “matron” and “cancelling contracts”. The very words of Middle Britain. How can you lose?

Here’s how.

Once upon a time Coca-Cola believed it was on to a winner. In focus-group tests, consumers said they preferred Pepsi. So you make Coke taste more like Pepsi. New Coke was born. And it was a fiasco. In his book Blink, Malcolm Gladwell explains why – consumers preferred Pepsi when they were asked to compare a sip of that drink with a sip of Coke. But when they drank a whole glass? Coke came out on top. Individual policies on immigration and hospital wards pass the sip test, but voters may not want a whole glass of fizzy populism.

Look at it another way. Politicians often wonder why people don’t vote. This is the wrong question. The real puzzler is why on earth anybody bothers voting at all. If you multiply the chance of influencing the outcome by the difference that a change of government might make to your life, you might calculate that the benefit to you is not enough to risk, say, that on the way to vote a caravan full of violins falls on your head, having been pushed off a third-floor council house balcony by a drunk dentist.

If a rational view of personal interest cannot explain people’s voting behaviour, what can? That they vote to make a statement about themselves. As the identification of party with class has declined, for instance, so has voting. By supporting a party, voters are declaring what sort of person they are. They want to be able to say that this is something they did for the country and they want their party label to declare that they are a good person, who does the right thing for the country.

A string of policy pronouncements may chime with individual preoccupations without satisfying even those who agree with them. Mr Brown could easily find in an election campaign that his message doesn’t work as well as the focus groups seemed to promise.

It might reasonably be objected that Mr Brown may not have crafted the perfect message but that doesn’t matter because he’s fighting the Tories and they are in a mess. Quite right. Except that it is not only the Tories he is fighting – it’s also the Government’s record.

The public have not made up their mind about Mr Brown. They are reasonably impressed with his handling of the various problems in the summer and reassured that he appears to be moderate and a human being. But they are very sceptical of new Labour politicians bearing gifts.

He says he is going to jail for five years those who illegally carry a gun. Where? He says contract cleaners will be sacked if they don’t meet cleanliness standards. Aren’t they now? He says he’s going to toughen up border controls. Yeah, right.

Mr Brown has excited expectations of change, but he cannot meet them merely by talking. He has to demonstrate change. And if he goes to the country now, he won’t have done. That’s why his poll lead is not stable. How long since he was last on even terms with the Tories? Er, a couple of weeks back, wasn’t it?

Of course, the Tories present a tempting target. It’s very hard to see them winning a majority in an autumn. But is it so hard to see them depriving Labour of its majority? There are serious contradictions in the Tory strategy. Perhaps even insoluble ones. A short dash to the polls might allow Mr Cameron to go to the country without even trying to resolve them. Anyone who can’t conceive of Mr Cameron appealing to undecided voters in a burst of television exposure is demonstrating a failure of imagination.

An autumn election? It is not hard to see Gordon Brown calling it in haste and repenting at leisure.

Times Recommends

• The ghost of Robin Cook haunts Chilcot’s feast
• The truth shouldn’t need oaths
• Violence: let’s separate the men from the boys