An election that was called ostensibly to strengthen the prime minister’s hand when negotiating Britain’s exit from the European Union has yet to deliver any insight whatever into Theresa May’s thinking on that subject. Mrs May was inscrutable when parliament was still in session and has buttressed that taciturnity with inane sloganeering on the campaign trail. The Conservative election strategy is to purchase as big a mandate as possible with the smallest possible expenditure in commitment and honesty about the challenges facing the country. This must not be permitted to continue.

Unfortunately, the Conservative electoral transaction appears to be available because the alternative candidate to be prime minister is Jeremy Corbyn. As Mrs May made clear in her response today to Mr Corbyn’s defence and foreign policy speech, the Labour leader plays a central role in Tory planning. In theory, a powerful recoil from Mr Corbyn will propel tens of thousands of voters into Mrs May’s arms.

Evidence from opinion polls and testimony from the doorstep in last week’s local elections suggests it makes tactical sense for the Tories to keep punching the bruise of public mistrust in Labour’s leadership. But there are hazards for the Tories in organising a bid for national power around the personality of the prime minister. Few dispassionate observers can doubt that the Conservatives are on course for victory on 8 June, yet there is a curious insecurity and a brittleness about the almost obsessional way they are trying to seal the deal.

Mrs May’s comfortable polling leads should afford the opportunity to secure a mandate for her personal vision of the nation’s post-EU future. That she prefers to keep that vision obscure suggests it is not yet formed. That the Conservatives are subordinating their party’s identity to the image of their leader also hints at lingering problems with the brand. The nation is being asked to put its trust in Team Theresa because Team Tory is not, by old repute, a very inclusive proposition.

The emerging personality cult around the prime minister is not yet sinister, but it is short-sighted. It is normal for leaders’ characters to be offered as proxies for their politics, offering a cultural signal of what they represent. A portrait of Churchill and the slogan “Help him finish the job” was one Tory pitch in 1945; “Confirm your confidence in Churchill” was another. That is what Mrs May hoped to achieve in an interview on the BBC’s One Show this week alongside her husband Philip. It was a banal conversation, not without flashes of warmth and character, but the aim was to present the Mays as a dull but dependable quasi-presidential First Couple.

There is nothing intrinsically shabby about using small talk to augment discussion of politics. Yet Mrs May’s campaign seems designed to belittle talk of what her politics actually are. For all her talk about being happiest campaigning on the doorstep, the prime minister’s public appearances are too stage-managed. Some of her press encounters have reportedly been vetted in advance for awkward questions. There have not been many unscripted encounters between the Supreme Leader and her people.

This approach can defer arguments and conceal divisions within the Conservative party, but it cannot eliminate them. While the prospect of a vague mandate is superficially appealing, there are senior Tories who recognise that opacity about intent in the campaign can become a handicap in office, never more obviously than on the details of Brexit. The public might reasonably reject policies that were never sold to them in advance. The manifesto, due next week, will certainly be slim but it should not be so vague as to raise suspicion that the prime minister is afraid to be candid about her agenda.

Mrs May is the popular choice when standing against Mr Corbyn, but that will not remain the context forever. If she is returned to Downing Street she will be judged by her actions, not by her capacity to be more plausible than a theoretical alternative. Then her failure to have spelled out in advance what another five years of Conservative government involve, especially the potential turbulence caused by Brexit, will haunt her. The proposition that everything will be fine if the people put their trust in the hands of one leader has been false and dangerous throughout history. It is also at odds with a parliamentary system whose lifeblood principles have always been challenge and scrutiny. Mrs May is doing well in exceptional circumstances, but she is not entitled to be treated as an exception to that rule.