Everything changes, but some things stay the same.

To watch the Queen addressing elderly survivors of D-day this week was to be reminded that the point of monarchy is constancy. All hell might be breaking loose around her, but there she is, dressed as she has dressed for half a century and choosing her words with the care she always has. She has seen enough prime ministers come and go that one more presumably doesn’t make much difference. The rest of us, however, cannot afford to be quite so sanguine.

Friday marks Theresa May’s formal relinquishing of the Tory leadership, which increasingly looks not so much like passing on the torch as dropping a burned-out sparkler and accidentally starting a grass fire. It will be almost the end of July before her replacement is foisted on the nation by those Conservative party members entitled to vote and, already, moves are reportedly underfoot to avoid the new leader facing a confidence vote in parliament. The will of the people has given way to the will of a few hundred thousand people who may barely represent Tory voters, let alone the nation. An awkward silence, meanwhile, shrouds the question of this unelected future prime minister’s democratic mandate.

There is an extraordinary moment in Jeremy Hunt’s new campaign video where the wannabe leader suggests Tories should choose him because otherwise there might have to be a general election that Jeremy Corbyn could win. “Vote for me, and hide from the voters” is a dismal slogan but less shocking than Dominic Raab’s refusal to rule out hiding from parliament too; this week he declined to reject hard Brexiters’ crazed pet idea that parliament be prorogued, or in effect suspended from sitting, to ram a no-deal Brexit through.

It would be government by carjack, almost certainly impossible in practice. But when a prospective leader can’t bring himself to say that this is the stuff of 16th-century monarchs not modern leaders, we slide towards that dark place where people who can’t get what they want by democratic means begin weighing alternatives.

Without wanting to be melodramatic, it’s in weeks like this that you realise how little stands between us and a prime minister of genuinely malign intent; how many democratic norms rely on an understanding that those in power will do the decent thing, or that the Queen will mysteriously intervene at the last minute. The assumption is that party leaders will always voluntarily seek mandates because otherwise voters would punish their high-handedness at the next election. But when the Brexit party didn’t even bother producing a manifesto, that most basic contract between politicians and the people, it feels unwise to take much for granted.

These are shark-infested constitutional waters, yet we’re sailing into them rudderless. May remains prime minister in theory, but government is on hold pending new management. The home, health and foreign secretaries among others are all in campaign mode, and anything the government does for the next six weeks will invariably get sucked into the vortex; there are already rumblings about the appropriateness of publishing updates on no-deal planning during the contest. When the EU extended our deadline for leaving, Britain was warned not to waste that time. Yet the only party leader who has used it to the full is Nigel Farage.

Votes in Peterborough are not yet counted. But whether the Brexit party gets its byelection scalp or not, the sidelining of the Tories in a marginal seat they held until recently has sent shudders through the party. There is no route to a majority for a Conservative party that can’t win a marginal seat even when its previous Labour MP goes to prison. But Farage’s party has been mischievously portraying the byelection as a fight between it and the Liberal Democrats, as if the two main parties barely existed; just hard leave versus hard remain, nothing but tumbleweed between. Playing up the Lib Dems in a Labour-held seat is, of course, a cynical ruse to split the remain vote by sowing confusion about where it should go. But as ruses go it’s clever, tapping into a profound exasperation with the big parties that has left smaller ones calling the tune.

Or more precisely, some of the smaller ones. If politics is now breaking open, then it’s not in the way a handful of Tory and Labour MPs envisaged when they abandoned their old parties to form Change UK, which this week duly split. They wanted to create something new but seem instead to have helped to revive something old, with the Lib Dems enjoying a popularity not seen since the days of Cleggmania as they reap the rewards of having fought Brexit before it was popular.

Facebook Twitter Pinterest ‘Farage’s party has been mischievously portraying the byelection as a fight between it and the Lib Dems, as if the two main parties barely existed.’ Nigel Farage at a Brexit party rally in Peterborough. Photograph: Danny Lawson/PA

But if the Tiggers failed to establish themselves as the answer, they were right to identify a problem with their respective old parties, and until Labour and the Conservatives have dealt with the underlying causes of their toxicity they have nothing to feel smug about. If the rise of the Brexit party continues, the change now coming might be the one some have long warned about: a vacancy opening up not in the centre ground of politics but the bigger space occupied by socially conservative voters, frustrated that their views have long been pushed to the fringe.

Polling voters on how they might react to new party leaders is notoriously unreliable because people struggle to guess how they’ll feel in the future about someone they don’t yet know. But with those caveats, polling leaked to the Boris Johnson-supporting Guido Fawkes site this week was instructive. Of five Tory candidates tested, Johnson emerged as most likely to stop votes haemorrhaging to the Brexit party, which is why he’s the frontrunner. But none of them won over enough Labour and Lib Dem supporters to cobble together a majority, with voters scattering in at least four directions. This is the stuff of nightmare coalitions and Faustian bargains. No wonder Tory MPs want to put an election off for as long as possible, in the vague hope something else turns up.

Labour is on the brink in Peterborough. This byelection is a battle over its future | Polly Toynbee Read more

In hyper-volatile times, it’s not completely implausible that something might. Small parties generally thrive when bigger ones screw up, which makes them vulnerable to bigger ones getting their act together again. If Corbyn finally settled on a Brexit position capable of scraping his own lost voters back off the Lib Dems, things could turn upside down overnight. If the momentum created by last month’s election upsets peters out over the summer, and a new Tory leader manages to steal the limelight for something other than Brexit, then the smaller parties might once again struggle to get noticed; their Achilles heel is supporters forgetting about them, or concluding that they’re a wasted vote.

But the deeper the Tories descend into a bidding war over a no deal, the more they make everything about Farage, and the stronger he consequently grows. If that is where this leadership contest is ultimately leading, then they shouldn’t be surprised when the people demand a say on it.

• Gaby Hinsliff is a Guardian columnist