No party is ever prepared for government, especially if it has been out of power for a long time. But David Cameron faces an unusual problem, in that he spent his first two-and-a-half years as leader of the opposition preparing to inherit a benign economy, and he has spent the last 18 months throwing all the levers into reverse. For the first phase, Cameron was the sunshine candidate, offering optimism and uplift. Heir not just to Blair but to Obama too, if not quite scaling those heights of excitement. In the latter phase, though, he has been forced to revert to Tory type, offering the electorate the unenticing prospect of fiscal discipline.
It was this confusion that snagged the launch of his long election campaign, with a poster that tried to be positive and negative at the same time. "We can't go on like this," it said, "except that we can when it comes to NHS spending" – or words to that effect. No wonder that the airbrushed photo of the Cult of Dave became an icon of contention: it was a symbol of tension beneath the surface.
Philip Hammond, the shadow Chief Secretary, put it concisely when I spoke to him this week. "Until 2007 we all thought that what we had to do was to finish Thatcher's unfinished business. She's gone down in history as an uncaring, economics first, last and only thinker. But she wanted to move on to education and what we now call broken society problems." Because of the recession, "to some extent we have got to tread the same ground, to fix the economy first". As the man in charge of making the Conservatives' sums add up, he knows better than most of his colleagues how difficult government will be.
The other thing that happened when the Tories launched their pre-election campaign is that several spending commitments were downgraded or disappeared altogether. It was not an elegant process, which was in part a tribute to the "prebuttal" operation run by Hammond's opposite number, Liam Byrne. Byrne and the Labour team produced a huge dossier costing Tory promises. Its greatest achievement was to use the ghastly political cliche "black hole" nowhere in its 150 pages. But its other success was to push the Conservatives into retreating from all manner of "sunshine" phase ambitions. In the headlong rout, Cameron's supposedly fixed intention to "recognise" marriage in the tax system came surprisingly close to an ad-libbed comedy sketch. One could imagine members of the Shadow Cabinet gathered around some Rorschach ink blots saying to each other: "Do you recognise that?" "It's a woman and a woman"; "Tuppence a week doesn't look like very much."
It is not all Francis Maude's fault. One of Cameron's greybeards – he calls them that, not me – Maude was a cabinet minister under Thatcher, and was put in charge of preparation for government. You would have thought that the plans would survive the scrutiny of a campaign launch. But Maude's position is like that of Neil Kinnock in 1990. Years of preparation to fight an election against the Great She-Elephant, She Who Must Be Obeyed, the Boudicca of the Poll Tax and suddenly Kinnock found himself facing a mild-mannered Acker Bilk fan from Brixton. The Labour Party had 18 months to recalibrate its strategy and did not succeed wholly. (And it is curious how long some grievances are held in the People's Party; when the plot broke last week one youngish Labour MP said bitterly to me: "I still haven't forgiven Patricia Hewitt for losing us the 1992 election." Her alleged crime was to make electoral reform the "last week" theme.)
We are facing, therefore, an election quite unlike any since the Seventies. Which may sound like a posh way of saying that it is likely to be closer – in terms of seats if not votes – but the reasons why are interesting. Peter Mandelson at the political Cabinet on Tuesday described the coming vote as a "change election". But it is not a change election like 1979, when the government appeared to have lost control of the economy as well as the public finances. Nor is it one like 1997, when the opposition offered the hope of a bright new tomorrow.
The Labour Party is having a collective nervous breakdown that sounds and feels like the collapse of the Conservative Party in the John Major years. I was a junior political reporter in those days and remember the corridors of Westminster when Tory MPs would take you into their confidence the moment you had exchanged pleasantries and discuss how to get rid of the Prime Minister. If you really wanted to know what the rebels were up to, you had to find Iain Duncan Smith.
Now it is Labour's turn. Until last week's attempted coup, Labour MPs were free with their private opinions that Gordon had to go. Before Christmas they said, "January", as if there were a plan. As soon as Patricia Hewitt and Geoff Hoon popped up, they said it was ridiculous idea. "Should have done it in June," they said, forgetting that at the time they had said that was a ridiculous idea because it would have meant an early general election. If you want to know what is going on behind the scenes in ministerial offices, read Norman Fowler's account of the end of the Major government, A Political Suicide, in which "power was tamely handed over by a party with an all-too-obvious death wish".
What is different this time, though, is that the Conservative opposition is nowhere near as popular as Labour were in the run-up to 1997. We are in the run-up to the anti-politics election, and it is a negative, life-denying, dismal prospect. I blame Tony Blair. The expectations he raised could never have been met, and their inevitable disappointment has drained the possibility of mounting a similar insurgency of optimism for a generation. That is not the only reason, of course. The switch from sunshine to austerity is a large part of it. And then there is the expenses issue. That was Cameron's deft response in a recent interview to the question why the Conservatives were not doing better in the opinion polls. The anti-politics fury over expenses has deadened the possibility of any party offering a "new politics" – a phrase that nevertheless still drops occasionally from Cameron's lips.
That could have been Nick Clegg's opportunity, as it was the Liberals' in 1974, when they advanced onto ground cleared by "a plague on both your houses". And the Liberal Democrats will do well at the election, retaining between 60 and 70 seats. But the fact that they already have so many MPs means that the expenses issue hit them too, and makes it harder for Clegg to pose as the insurgent clean-up force from outside the Westminster club.
So, prepare for a negative campaign in which no party will be able credibly to offer a clean break. Mandelson is wrong: this isn't a change election, it is a retrenchment election. The advantage of that, from Cameron's point of view, is that expectations of him will be low and he has a chance of exceeding them. The disadvantage is that he has not had time, and shows no inclination, to prepare a cuts programme for government and seek a mandate for it.
John Rentoul is chief political commentator for The Independent on Sunday