Nicholas Hytner’s terrific reimagining of Julius Caesar at London’s Bridge theatre is a topical reminder that political assassinations are often messy and frequently don’t have the outcome that the plotters intended. In the name of saving the Roman republic, Brutus and his comrades stab – or, in the lively Hytner version, gun down – Caesar in the senate. Only to unleash a brutal civil war that sets things up for his adopted son, Octavius, to become Rome’s military autocrat and first emperor. Not what they meant to happen at all.

There is a possible moral here for Tory MPs as their clammy fingers hover over semi-unsheathed daggers and they contemplate whether to put Theresa May out of her misery. The Tory tradition, rather like the Roman way, has been dictatorship tempered by regicide. Tories are slavishly loyal to the leader right up to the moment before they slash the toga. That, at any rate, was how they used to operate. In the joyless era of Mrs May, the Tory party has adopted a new and much less satisfactory method of dealing with a floundering chief. This is to be openly disloyal to the leader and engage in endless discussion about dispatching her without actually going through with the deed. The ides of March come round every day. The enemies within her party who accuse Mrs May of being indecisive and incoherent share those traits with the object of their dismay.

Much of this is her fault. She has not recovered from throwing away their majority with her atrocious election campaign in June last year. In the immediate aftermath of that self-inflicted debacle, I wrote that she was “a zombie prime minister” doomed to spend the residue of her time at Number 10 “in office, but not in power”. At the time, I wondered if I had been a bit too savage, but subsequent events have only made the description seem more apposite.

She has created few opportunities to revive her authority and bungled those that have come her way. An attempted relaunch of her premiership at the party conference is remembered only for the coughing fit that was accompanied by the set falling apart. The new year reshuffle, billed as an enterprise that would re-establish prime ministerial authority over this quarrelsome government, ended up exemplifying her weakness when she dared not face down some middle-ranking cabinet ministers who simply refused to move. More damaging in the eyes of some Tory MPs was the revelation of a selfish impulse to put her own short-term needs above the longer-term requirements of her party. Anyone from younger generations of Tories who had been identified as possible future leadership material was either overlooked or shunted into a ministerial post in which they would find it difficult to shine.

The discontent with her leadership usually begins with the mess over Brexit, but does not end there. A growing chorus of complaint, from MPs of different ideological flavours, wails that her premiership displays no purpose beyond day-to-day survival. Nor does Downing Street show any capacity to embrace fresh thinking when it is offered by others. “No one in her immediate circle is interested in policy. There is no intellectual engagement,” complains one former cabinet minister. Another Tory MP describes Number 10 as “the place where good ideas are sent to die”.

Voices in Brussels and around Whitehall are beginning to murmur that if there is going to be an attempt to remove her, it would be better it happened sooner rather than later.

It takes 48. That many Tory MPs have to ask for it to trigger a vote of no confidence. No one but Sir Graham Brady, the chairman of the backbench 1922 committee, knows how many of his colleagues have written to him demanding such a vote. The speculation among Tories is that we have got closer to the magic number since the new year. If Mrs May then won a confidence vote, she might carry on, more or less damaged, depending on the size of her victory. Only if she lost – or won by a fatally narrow margin – would there be a contest for the succession.

It is this next step that shivers the spines of a lot of Tory MPs. There are some who have concluded that things have become so bad that it is worth taking the risk of unleashing a chaotic and vicious contest to succeed her. But it is worth noting that there are also Tories who have travelled in the opposition direction, MPs who once thought she had to go, but who now calculate that the consequences would be too awful. One former cabinet minister remarks: “Where I was in favour of her departing immediately after the election because she had lost all authority, now I think it would be a disaster and a bloodbath.”

Mrs May should be most wary of the Cassius-like men with a “lean and hungry look” among the hard Brexiters

The soft Brexit wing of the Tory party fears that any replacement would likely be worse. A leadership contest would be decided by the membership. We can’t be exact about how many of them there are – because the numbers are too embarrassing to publish – but well-informed estimates suggest that Tory membership has fallen to below 70,000. We know from the valuable work of Professor Tim Bale at Queen Mary University of London that they are rather elderly, predominantly male and overwhelmingly in favour of hard Brexit.

Their most popular pin-up is Jacob Rees-Mogg, a man who has acquired a cult following among Tory party members without ever being encumbered by any experience of ministerial office. He would struggle to succeed because many of his parliamentary colleagues think he would be electoral hemlock and it is Tory MPs who decide who gets into the final two put to the members. But that he does so well in polling of activists tells us that a contest now would not look promising for any candidate who was a Remainer.

The present danger to Mrs May largely comes from the hard Brexiters in her party. They liked her when she was echoing a lot of their rhetoric about Brexit. They have become progressively more disenchanted with the drift of the negotiations. What most of the rest of us might see as an accommodation with reality, they regard as mounting betrayal. Mrs May should be most wary of the Cassius-like men with a “lean and hungry look” among the hard Brexiters – or the plump and hungry one in the case of Boris Johnson.

To describe the state of play within the Tory party is also to illustrate why it can’t all be blamed on the failings of one woman. It is an almost universal complaint that Mrs May won’t be precise about what sort of end state she seeks for the future relationship with the European Union. A promised speech, trailed as an event that would bring clarity to what she wants from the negotiations, has never materialised. Yet you can see why the prime minister ducks her fearful head below that dangerous parapet. She acquired the leadership in the first place because she has never taken a definitive stand in the civil war over Europe. Clarity about her intentions means combustion. Move towards a softer Brexit and the hard Brexiters will detonate. Tilt in the direction of a harder Brexit and the soft Brexiters will explode. Any new leader will face exactly the same problem trying to bridge the irreconcilable contradictions of the Tory party, which is why most of the contenders for the succession would still rather the vacancy opened up after March 2019.

A new leader would not change some other fundamentals. The Tories do not have a proper majority in the Commons. They are deeply divided over the future direction of their party. If Mrs May struggles to describe a renewal project, it is not just because she lacks the vision. It is also because her party, split between modernisers and traditionalists, cannot agree with itself about what form renewal should take. She is as much symptom as she is source of their maladies.

Theresa May is a highly flawed and extremely enfeebled prime minister, and the Tories will almost certainly be rid of her before the next election, but they are kidding themselves if they think all their troubles begin with one woman and can be ended simply by taking their knives to her toga.