Tory MPs know that repetitive disloyalty and conspicuous party division hasten electoral defeat. Yet they cannot line up obediently behind David Cameron. The refusal by more than half of them to accept the Prime Minister’s moral lead on gay marriage cannot be explained away by his granting of a free vote in parliament. It expresses a more profound reluctance to be led.

It follows that some Conservatives either do not care if they lose the next election or are actively pursuing that outcome. That is less bonkers than it sounds. Coalition has deprived many Tories of any sense of ownership of the government’s programme (as well as suffocating their ministerial career prospects). As their first loyalty is to the idea of being Conservative and that creed is not, in their view, paid proper respect in Downing Street, they already feel themselves to be in opposition. The usual explanation for backbench anger starts with Cameron’s failure to deliver the election triumph that was advertised asthe party’s reward for swallowing sickly “modernising” medicine. Another way of looking at the Conservatives’ problems is not as an aftershock of defeat but as a failure to adapt to victory.

The lack of a majority has hardly limited Cameron’s ambition. The coalition has turned public services upside down while imposing the tightest budget squeeze in a generation. Labour is doubly confounded. The opposition lost the economic blame game in the opening months of the parliament. Only slowly are voters beginning to cite George Osborne’s policies over Gordon Brown’s legacy as the bigger cause of their pain. At a deeper level, the left is affronted that a crisis in capitalism has somehow generated a Conservative chancellor.

That dismay is an extension of Labour’s discomfort with its own record. There is near consensus in the party that Brown and Tony Blair were too deferential to Big Money. Their accommodation to Margaret Thatcher’s economic legacy is seen as an intellectual surrender. Ed Miliband has no appetite for pursuing the “Blairite” model of public-services reform, with its emphasis on markets and competition. So the coalition has snatched that baton and giddily run off with it: churning out academy schools; having GPs shop for private treatments on behalf of patients; outsourcing welfare-to-work schemes and prisoner rehabilitation.

Throw in Labour’s vague acceptance of the need for budget constraint and it seems as if all the big battles are being waged on Conservative terms. Miliband’s “one nation” alternative looks like rhetorical homoeopathy – balm that comforts only those people with a predisposition to believe.

If Conservative ideas have the run of West­minster, why does Cameron look like he is losing? The obvious answer is that the ideas aren’t working. The economy is stagnant. The subtleties of public-sector reform are lost in unsubtle cuts. Most people’s experience will be of fewer and worse services.

Downing Street is still confident that the economy is poised for recovery and that time is running out for Miliband to define himself as anything other than a whingeing spectator. Cameron’s problem is that Tory MPs are not minded to accept their leader’s invitations to wait patiently for fresh political winds to carry them to victory.

While the left sees Cameron’s ultra-Blairism as proof of ideological zeal, the right banks it as technocratic continuity from the old regime and urges more radicalism, with more aggressive assaults on Whitehall control. Labour regards Osborne’s austerity plan as dogmatic butchery but noisy Conservative dissenters say spending and borrowing are still out of control. They want deeper cuts and lower taxes. Cameron cannot acquiesce to that demand without abandoning all pretence of centre-hugging moderation, the defining ambition of his leadership.

There is something absurd in the complaint that the Prime Minister is inadequately Conservative when he is implementing so many Conservative ideas – market reforms, deregulation, shrinkage of the state – in impeccably Conservative fashion. But Cameron is not a natural thumper of ideological tubs. His Toryism is instinctive and uncodified. He struggles to proselytise for his beliefs because, taking them as part of the natural order, he has never interrogated them with much rigour. Cameron’s hope of remaining Prime Minister rests on the belief that British voters will endure austerity if it is sold to them by a charming, mild-mannered gentleman who insists politely that there is no alternative.

He stands for business as usual, only poorer than usual. It is not a cheery proposition but it may be the Tories’ best chance of clinging to power. Cameron imagines himself to be a visionary leader but in reality his appeal is to that stoical strain in British culture that takes what it is given, makes do, muddles through and apologises when its toes are trodden on.

Backbench Tory MPs are not so deferential. They want ideological insurgency, not managed decline. There is no agreement over what new direction the party should take – more liberty, or social reaction? Whatever the change, all want it to be harder and faster. That is not something the Prime Minister can deliver in a coalition. Besides, it is not his style. Cameron sold himself to his party and the country as the first 21st-century Conservative leader. In truth, he represents the ultimate valediction of 20th-century Conservatism – the candidate you might cook up in a laboratory with political grafts from Harold Macmillan’s patrician elitism, Margaret Thatcher’s economics and John Major’s nostalgic moralism.

If his party thinks that is a monstrous creation, it faces a huge task working out what it wants to be instead. It is the kind of work that can only be done in opposition.