There is nowhere better to plot than the Palace of Westminster. There are alcoves to conspire in, little-used corridors and discreet watering holes. And no group enjoys plotting more than Tory MPs. Add a general election result that made the Tory leader a lame duck and you have the perfect ingredients for political mischief. But the Tories aren’t just plotting against Theresa May — that would be too simple, since her departure is a question of when not if. Nor is the principal conversation about who the leader should be. No, for a Tory the first stages of any leader-ship battle is to identify who they don’t want and then to set about destroying them.

No one is more plotted against than Boris Johnson. When I asked one well-connected minister who he was backing for leader, he replied, ‘Whoever will stop Boris getting into the final two.’ The Foreign Secretary’s detractors in parliament — there is no shortage of them — are determined to leave nothing to chance. Tory party rules mean the final two candidates must fight a campaign among the members in the country, which would suit Boris’s campaigning style. So they intend to stop him long before it gets to that stage.

Since the election, Tory MPs don’t agree on much. Yet there is near unanimity on the need to avoid another general election any time soon. ‘One thing the cabinet is united on is that if she wasn’t there and there was an election, say in a year’s time, we’d lose,’ one Secretary of State tells me. The belief that going back to the polls would be a disaster for the Tories is what is keeping May in place. Patience with her is limited, though, and the party’s conference in October is being seen as a deadline. A well-placed source tells me, ‘If there’s no timetable at conference it will wind people up. People want an indication of when she’s going.’

The holding answer as to when May will quit is when the Article 50 deal is done, so sometime by March 2019. The feeling is that this is a logical end-point to her premiership, preventing a Tory leadership contest where Brexit could render the party asunder, and suiting nearly all of the leadership contenders, Boris included.

However, there are renewed doubts in the party hierarchy that May can last until then. The idea of senior members of the cabinet agreeing on the right successor to May is taking hold again. But it’s hard to see Philip Hammond, David Davis, Amber Rudd and Boris Johnson reaching any agreement. It’s always possible that events — or the party conference in October — will thrust a hitherto underestimated candidate on to the centre stage.

David Davis is one senior member of the cabinet who would be acutely disadvantaged if the leadership contest didn’t take place for another two years. The 68 year-old is currently the Brexit secretary, and in any contest in the near future could present himself as the candidate best placed to hit the ground running. But once the negotiation’s finished, the rationale for his candidacy is diminished. May’s closest allies are desperately trying to work out just how significant it is that his friends, notably Andrew Mitchell, are on manoeuvres. One Downing Street source tells me, ‘Davis and Mitchell are as close as you get to a genuine friendship in politics. So the fact he’s doing it does worry me.’

The case for May going sooner rather than later is that she is too weak to do the Brexit negotiations. The European Union, aware of her domestic troubles, will try to push her around. Her threat to walk away is no longer credible and so the chances of a bad deal have increased. If Brexit goes wrong, the Tory party will be held responsible, and will suffer a defeat worse even than the 1997 general election. It is also said that as long as May remains, there can be no Tory recovery or renewal. The party is stuck in a holding pattern while Jeremy Corbyn’s momentum goes unchecked.

Those pushing for Davis make two other points in their attempts to get Tory MPs to bite. The first is that the fixed-term parliament act essentially means there can’t be an election unless the Tories vote for one. So there’s no need to worry that a leadership contest would lead to the public returning to the polling stations.

The second point is designed to appeal to the middle-aged men in a hurry who dominate the junior ministerial ranks. It is that May is too weak to do a proper reshuffle, so there’ll be no clearout of the cabinet. With no departures, there can be no new arrivals. A few heads have already been turned by that thought.

What, then, is the case for Davis? It is, essentially, that he is a pragmatic Leaver who can get the right of the party to accept the necessary compromises. He is, his admirers contend, the De Gaulle of the situation, the man who can say ‘Je vous ai compris’ to the Brexiteers. The domestic political proposition is that he is well suited to taking on Corbyn. He is, his supporters argue, an ‘authentic politician’, and as a council estate boy, can’t be dismissed as a Tory toff. The final, unspoken point in his favour, is that he is 68 and has been in parliament for 20 years. No one would be conceding their chance of ever being leader in future by voting for him now. I understand, however, that if Davis were to run he wouldn’t see himself as a stopgap, but rather as someone who’d take the Tories into the next election.

But David Davis is about to find out what Boris Johnson knows to his cost: you don’t want to be the frontrunner in any Tory leadership contest. As soon as you are, you have a target on your back. (If I had a pound for every Tory who in the past few days has pointed out to me that Davis voted against gay marriage, I’d have enough for a punnet of strawberries on Centre Court.)

Boris, though, has had it even worse than most frontrunners. His problem is that there are not one but four groups who have it in for him. The Cameron/Osborne gang will never forgive him for ending the career of both their king and their dauphin, and they are determined to stop him claiming the crown. Their desire for vengeance blinds them to the fact his liberal Toryism means he is closer to the Cameron project than nearly any of the other contenders.

The second lot are the Tory Europhiles who blame Boris for the referendum result. Then come the May ultras, who regarded Boris as the most immediate threat and so put him in the frame for leadership in order to make him an obvious target. Then there are the men of government who are offended by his unconventional path to one of the great offices of state; I am told that Philip Hammond is ‘obsessed by Boris’. It is little wonder that even the Foreign Secretary’s friends have been reduced to declaring that ‘every-one’s out for Boris’.

Not all of Boris’s problems can be put down to referendum bitterness or tall poppy syndrome. In many ways, he is not helping himself. He is still making too many unforced errors. His spectacularly bumbling Eddie Mair interview was harmful because it played up to the clownish stereotype of him that his opponents want to present. Boris’s ministerial enemies claim, unfairly, that he is shambolic both in cabinet and on the international stage. When Boris mucks up a media appearance, he makes these distorted reports seem more credible. His timing has been off too. His team’s intervention on public sector pay infuriated Tory MPs because it looked like he was jumping on the bandwagon, putting his own interests ahead of the party’s.

Boris’s Falstaffian coming-of-age moment is overdue. Even those Tory MPs who are well inclined towards him want some sign that he has put aside childish things, that he is surrounding himself with serious people. Yet Boris cannot bring himself to say ‘I know thee not’ to some of the less impressive characters who have attached themselves to him in the hope of preferment. That’s an admirable kindness, perhaps, but a great flaw in a politician.

At the same time, Boris needs to get to know his colleagues better, given the tactical voting that will be organised against him. He will need the support of 106 Tory MPs to be sure of making it to the final round. But as one of those who knows him best observes, Boris doesn’t make friends — he receives offers of friendship. The result is he remains a stranger to far too many Tory MPs. When he recently made an appearance on the House of Commons terrace, parliament’s prime spot for summer socialising, it was the first time that most MPs had seen him there.

Margaret Thatcher said at Ronald Reagan’s funeral that the late president embodied the great cause of cheering us all up. Boris used to have that quality, but it has been in abeyance in the last 12 months. His critics claim he can never recapture it after the referendum — he has become too divisive a figure. Boris himself seems to have lost some of his joie de vivre. He has taken to waking up at 5.30 a.m. to read the papers online and, too often, also the angry comments about him, a dispiriting experience for anyone. Boris’s chances of cheering the rest of us up are not improved by his preoccupation with how many friends he has lost because of the ‘apple of discord’ that was the Brexit referendum.

Is it all over for Boris? Not yet. He has a skill that very few other front-rank Tory politicians have; a genuine love of being out in public and campaigning. During the election, the only times the Tory campaign had any sense of energy about it were the rare moments when Boris was allowed centre--stage. He also has an almost unrivalled capacity to communicate; his language resonates. These abilities mean you can never rule him out, as even Tory MPs who don’t instinctively admire him admit. ‘The Tory party will only turn to Boris when it is three-nil down and there are only 15 minutes to go,’ one person who knows the party as well as anyone told me during Boris’s first term as mayor. Well, by 2019, the Tories could be at least three down.

The most successful politicians can present themselves as authentic in multifaceted ways. Barack Obama was an educated lawyer and a black community organiser; David Cameron was a Tory toff whose wife worked and who was dependent on the NHS for his child’s medical care; Ruth Davidson is a lesbian, an army reservist and a practising Christian. Boris used to be the darling of the shires who had twice won in a Labour city. He needs to find a way of showing that he still has that quality.

The Tories are now engaged in a long leadership campaign. Boris Johnson cannot afford any more slip-ups, and the party should remember that if it carries on with its game of destroying every frontrunner who emerges, they might find they have no one left to beat Jeremy Corbyn.