“If we are victorious in one more battle … we shall be utterly ruined.”

Like the good intellectual that he’s vigorously pretended not to be of late, Boris Johnson will probably know that line. It’s from the Greek historian Plutarch’s account of the battle that gave us the phrase “pyrrhic victory”, the kind of victory won at such cost that you almost wish you’d lost.

In theory, Johnson woke up on Friday morning having won the war. After David Cameron’s announcement that he would step down come October, Johnson is now the heir presumptive – albeit at this stage very presumptive – to the Tory leadership, perhaps only four months away from running the country.

He has everything he ever wanted. It’s just that somehow, as he fought his way through booing crowds on his Islington doorstep before holding an uncharacteristically subdued press conference on Friday morning, it didn’t really look that way.

One group of Tory remainers watching the speech on TV jeered out loud when a rather pale Johnson said leaving Europe needn’t mean pulling up the drawbridge; that this epic victory for Nigel Farage could somehow “take the wind out of the sails” of anyone playing politics with immigration. Too late for all that now, one said.

The scariest possibility, however, is that he actually meant it. That like most of Westminster, Johnson always imagined we’d grudgingly vote to stay in the end. That he too missed the anger bubbling beneath the surface, and is now as shocked as anyone else by what has happened.

“People talk about reluctant remainers, but I think there have been a lot of reluctant Brexiters around, people who voted leave thinking it wouldn’t happen but they’d be able to vent and to tell all their friends at dinner parties they’d done it,” said one Tory minister.

“He thought what all those reluctant Brexiters thought: it would be a vote for remain, he would be seen as having stood up for a principle.” After which leave’s newest martyr could simply have bided his time for a year or so before being triumphantly installed in Downing Street.

It’s perfectly possible, of course, that the Tories on both sides who suspect Johnson was never an outer in his bones are plain wrong, that the anonymous Labour MP who hotly accused him on Friday of jeopardising thousands of ordinary people’s jobs just to secure one for himself was doing him a terrible injustice.

Perhaps Johnson really did have a last-minute epiphany, declaring for leave in the sober realisation that this was always how it might end – Scotland demanding independence, Northern Ireland’s fragile political settlement at risk, Marine Le Pen jubilant, the Bank of England stumping up £250bn to stabilise the market. Perhaps he’s still convinced all will be fine eventually.

And let’s hope to God he’s right. Any remainer who doesn’t pray to be proved wrong about Brexit is callous, wishing disaster on people who are unable to afford it. But right now, what scorched earth Johnson stands to inherit – a nation febrile and divided, teetering on the brink of economic and constitutional crisis. It’s all over for David Cameron now. But it feels, too, like the end of a broader modernising movement to which both he and Johnson belonged.

The deeper fear among Tory remainers now isn’t just of a recession. It’s about the rise of something new in British politics, unleashed when politicians with scant respect for truth meet desperate voters; and for the backlash to come, when it sinks in that Brexit hasn’t ended immigration overnight or magically given depressed communities their futures back. Already, one wonders what those who voted desperately for change make of being told there’s no rush to invoke article 50.

No wonder Tory leavers wanted Cameron to stay for a bit while they scratched together a plan for dismounting safely from the tiger they’ve been riding. But control is what the Brexiters said they wanted. Now they’ve got it, and they’re about to find out how it feels.

It’s not over yet, of course. There are plenty of Tory MPs grimly determined to make them pay for whatever dark furies they have helped unleash; to lie down in front of the Boris bulldozer.

The obvious name flying around the “anyone but Boris for leader” camp on Friday morning was that of Theresa May. Some of those who backed George Osborne before the chancellor knowingly burned what remained of his ambitions by publishing that fantasy Brexit punishment budget will now back her, as will some Tory women worried that female voters distrust the philandering Johnson.

The women’s minister Nicky Morgan is also testing the water, but May probably has a headstart. The home secretary’s mysterious absence from the airwaves during the referendum campaign disguised a fair bit of local-level campaigning for remain, reaching activists likely to support her.

There is also the glimmer of an alternative emerging in Stephen Crabb, the work and pensions secretary endorsed by his good friend the Scottish Tory leader Ruth Davidson, who leads a small but interesting group of working class Tories keen to tackle the economic insecurity exposed by the Brexit vote.

But he’s a relatively unknown quantity even inside Westminster, let alone outside. The blunt truth is that nobody else in Conservative politics gets begged for selfies as Johnson did on every walkabout; none has his charisma or his reach. If his name is on a shortlist of two put forward to Tory members, few doubt he would be the runaway winner.

And if MPs conspire to keep him off that list during the preliminary stages of the contest? Well, imagine the consequences for those who have already outraged constituents by voting remain. Imagine the rage, the mass defections to Ukip, were Johnson to be seen to be blocked by yet another elite afraid of ordinary people getting it wrong.

So don’t imagine his colleagues haven’t noticed Johnson’s casualness with the facts during this campaign, or the unsavoury company he sometimes kept. Don’t think they don’t resent an old Etonian journalist on £250,000 a year playing the anti-establishment hero, or hope for something else to turn up. But don’t imagine either that some aren’t wearily wondering if this couldn’t be made to work.

Johnson is far from a buffoon. He’s an agile thinker, gifted communicator and natural opportunist who made a reasonable fist of governing London after recruiting some reliable deputies (enter Michael Gove). He’s smart enough to have learned from the recent Labour leadership campaign – in which managerially competent candidates were slaughtered for being on the wrong side of a visceral grassroots argument – that elites only survive in this febrile climate by pleasing the masses. Perhaps somehow it will all come together.

It’s just that on Friday morning Johnson didn’t look like a man with a plan that’s all working perfectly. He looked more like a king unable to take more such victories.