For some time now, Conservative strategist Lynton Crosby has been reassuring his adopted party they will reach “crossover”. This is the term he’s been using to describe the moment when they take over the lead from Labour in the polls and push ahead.

The date of crossover, rather like the rapture, keeps being pushed back. It was meant to be Christmas last year, but nothing of significance happened then apart from a particularly good Dr Who special. January was also disappointing, February was frigging desolate and March passed without a squeak. Now we’re in the middle of April, what TS Eliot described as “the cruellest month”: for the Tories that’s proved true, with Labour and Conservative still stuck on more or less 33%.

It would be easy then for David Cameron to give up on Mr Crosby and his promise of good polls ahead; except, he can’t. Lynton Crosby is his Designated Bastard, the man his party has paid fistfuls of money to order all of them about and get them to do whatever it takes to win. It’s the stuff of tradition for Tory governments to get in an expensive Designated Bastard at election time; it’s the line of life, a cycle of comfort. The Designated Bastard arrives, tells them not to be pussies, puts up posters about Labour’s tax bombshells, flashes up cartoons of the Labour leader in the pocket of someone, or being the poodle of someone, sitting on someone’s lap, wearing someone’s hair, or being stuck up someone’s arse.

Usually, the party pays devoted attention to the Designated Bastard. First, because he’s so expensive but really because he’s such a Bastard. He gets them to do things they’ve spent the past five years being ordered not to under any circumstances. For five years, they’ve been clenching their teeth and talking about partnership and coalition. They’ve been pushing Big Societies and feeling everyone’s pain by sobbing that we’re all in it together.

Then the Designated Bastard comes along and tells them it’s OK now to junk all that, to accept that most of us voters are mean and self-interested, and that any appeal to our immediate material needs and to our deepest fears will work. The Designated Bastard will explain to them that to win, they’ll need to ignore those who won’t vote for them, and, if need be, to legislate against them. If it involves pushing welfare cuts for the young unemployed in order to pledge cuts to inheritance tax for the wealthier, then that’s what needs to be done. If it involves tempting council home occupants with the right to buy, at the expense of an already depleted social housing market, then it’s just tough teats to everyone. He’s a Bastard and he’s just telling you what you already know but never thought yourself capable of: you need to go in and display your inner Bastard to your constituents. It’s always worked and like the sun coming up it will happen again.

Except, this time, it seems not to be. Lynton Crossover hasn’t worked. And that’s a problem, since there is no plan B. The Tories believe in tradition and the tradition has always been that being a Bastard works. So panic sets in. Once panic starts, rational political behaviour falls apart. Hence the true “crossover” we got last week – the much commented on swapping of clothes brazenly taking part in the Labour and Conservative manifestos. Labour painted themselves as the party of fiscal rectitude, while the Tories went crazy on uncosted spending commitments. In this crazy looking-glass politics, Labour turn out to be the party with the most conservative financial commitment to the NHS, while the Conservatives are the most profligate.

This muddle has been a long time coming. For decades now, each main party has been defining itself on how similar it is to the other and how different it is from its own past. New Labour stole Thatcherite prudence and Cameroonian Conservativism detoxified its nasty image by going green and socially aware. Like two galaxies drawing closer to each other, it’s no wonder they ended up in a massive swirl of confusion. The spinning can’t be stopped: if anything, it gets faster and faster until you can’t tell which one is which.

Labour’s paranoia about looking like Old Labour I can understand: battered for so long by a mostly rightwing press, it still clings to a suspicion that even in this digital age the old tabloid headlines still affect people’s opinion. The Tory volte-face I find truly extraordinary, though. Normally, this type of trickery is done with just words. Last election, it was the verbal gymnastics contained in such slogans as “Vote Blue, Go Green” or that most perfect of semantic paradoxes, “Vote for Change: Vote Conservative”. It’s a basic trick with words, in which you take a word and insist it means its opposite. The more you insist, the greater chance people will believe you.

This time round, though, there is something desperate about the trick. They will “spend” on the NHS more than Labour, but that spending will be funded by carrying on with their “track record” on the economy. They’ll block Scottish MP’s voting on certain tax laws but that will somehow keep the UK united. They will rail against recklessness, but concede a European referendum to stave off a threat to their support and pledge billions in public spending based on no more than an inkling the economy’s going to keep growing.

All this time, they’ll muffle this panic with words such as “steady” and “on course”, words used to conceal an unsteady veer away from stability. They’re like bad magicians who, at the moment of subterfuge, simply shout: “What’s that?” and point to the other side of the room in the hope we’ll turn away.

This isn’t wordplay – this is charlatanism pure and simple. David Cameron is indulging in basic quackery, trying to sell you stuff he knows doesn’t work. He’s doing it with our money and he’s conjuring with people’s lives. We know there’s no magic; the money will come from the cuts and deficit reductions and benefit targets and financial squeezes on those Cameron knows won’t be voting for him anyway. It’s the bastardly misuse of the public purse and the final proof, if any were needed, that he is unfit to lead his country and his party unfit to govern.

Armando Iannucci’s credits include The Thick of It, In the Loop and Veep. He is writing a series of pieces for the Observer in the run-up to the general election