So far, we know that the Vote Leave campaign reached its spending limit before it reached the end of its money, and funnelled £625,000 into BeLeave, as well as £100,000 into Veterans for Britain. We have been told, thanks to the testimony of Shahmir Sanni, that this money didn’t even touch the bank account of BeLeave.

One piquant detail is that Sanni had been working as a volunteer, first for Vote Leave, then for BeLeave, and had hoped that this last-minute cash influx might pay for his train fares, only to find that it went straight to AggregateIQ, the data firm with links to Cambridge Analytica. If there’s a more poignant vignette about the exploited millennial – first they use his free labour, then they out him in public, then they contradict him, and they wouldn’t even stand him a Pret a Manger sandwich and a travelcard in the process – I can’t think of it.

The argument appears now to hinge on whether or not Vote Leave continued to coordinate with BeLeave. In his rebuttal, Stephen Parkinson (once Vote Leave, now working for Theresa May) released an official statement from No 10 saying that he had met Sanni through a mutual friend at university – a claim disproved by the email trail in which Sanni introduces himself through the whistleblower Christopher Wylie. Parkinson also said, in another official statement that has now been removed, that any advice given to BeLeave was in his capacity as Sanni’s “date”.

Play Video 10:25 The Brexit whistleblower: 'Not cheating is the core of what it means to be British' – video

It’s a cliche, it’s been on The West Wing, everybody knows it and yet that doesn’t dent its wisdom: when a scandal breaks, the only thing to do is tell the truth, tell all of it, tell it straight away. In real life, though, this is not what happens. Instead the scandal is dismissed, the dismissals fall apart, the scandal begins to look more serious, the tone plummets, and by the time you know exactly what happened, the event has become a carrier issue for a broader debate: what kind of person are you?

Are you a privacy and transparency kind of person, or a win-any-way-you-can kind? Are you the kind who thinks we’re all being controlled by new media we can’t hope to understand, and the turbulence of the world is merely a reflection of this new wild west? Or are you the kind who thinks a few bob here and there couldn’t possibly make a difference to a result, that people aren’t idiots, and if everyone believed everything they read on Facebook, we’d all have a pair of Mahabis slippers and wake up every morning making a list of the things we’re grateful for?

On what grounds would the referendum result remain valid? And if invalid, is there any alternative to a second one?

Those fault lines, as vital as they are for the heating up of divisions that make our current politics so spicy, are diversionary. The use of personal data, its ethics and efficacy, is fascinating but separate. The immediate importance of this story is whether or not electoral spending limits were breached. The harmonised chorus telling investigators – including the Observer’s Carole Cadwalladr, Channel 4, Jolyon Maugham’s Good Law Project – to stop digging has many melodies: that no breach occurred; that no amount of money could have bought this “overwhelming” result; that the electorate is bored of talking about the referendum and just wants done with it; that the Electoral Commission has already investigated twice. There is truth to every argument, in amounts varying from absolute-but-irrelevant to homeopathic, but none makes any difference to the substantive case. If we believe that democracy is made meaningful not by aerated statements in its praise but by the rules that govern its execution, and if we believe there’s a chance that those rules have been broken, it would be incurious not to check.

Facebook Twitter Pinterest ‘A mirage of coherent analysis in a desert of nonsensical assertion.’ Shadow Brexit secretary Keir Starmer yesterday. Photograph: Darren Staples/Reuters

We can guess the shape of the next argument because it will be exactly the shape of the argument over every other hurdle to Brexit: Northern Irish border? The people have spoken (but … but what about Irish people?) Freedom of movement? The people have spoken. The referendum was an earthquake, a revolution, a surge of anger against the establishment by an honest and passionate populace. Defy them on a technicality? There’ll be blood on the streets if you do.

With a regularity that should be breathtaking but of course, being regular, no longer is, rules and laws are portrayed as the nefarious and opaque means of returning power to the hands of the authorities, whence “society” successfully wrested it 21 months ago. Yet a lawless discursive terrain, one in which rules can be fuzzed away with a deeper appeal to feelings, is nothing more than inept, early-stage authoritarianism.

Yesterday, Labour’s Brexit spokesman, Keir Starmer, gave a speech in Birmingham that was like a mirage of coherent analysis in a desert of nonsensical assertion; as unusual as it was, in that its arguments were supported and their evidence verifiable, its true distinction was practical. Starmer means to introduce an amendment to the EU withdrawal bill: should the government be defeated on the deal it brings back in October, it must then be for parliament to decide what happens next. The coming 20 years are too important to be decided by an executive that can’t even make its mind up about fish. The current choice – vote with the government or crash out of Europe, or, to give it its full Noel Edmonds title, deal or no deal – fails to meet any basic standards. It is, paradoxically, both dry and terrifying to see politics reach this pitch, where the future of so many can rest on the success or failure of an amendment.

Vote Leave members 'may have committed criminal offences' Read more

That, ultimately, is the nature of the rule of law: like a seatbelt, it’s not interesting until you need it. Disasters aren’t averted by equally passionate forces hurtling from the other direction; rather, by the sober measures put in place in calmer times, to ensure that heady rhetoric and base cash at least undergo the scrutiny and challenge of representative democracy before they carry the day.

All parliamentarians, leave and remain, need to ask themselves what it means if Vote Leave broke the electoral rules: on what grounds would the result remain valid? And if invalid, is there any alternative to a second referendum? All of them, leave and remain, need to ask searching questions about the role of parliamentarians if it is not to shape the coming negotiations with Europe, when May and her team run out of the ideas that are already flimsy and mutable.

The first step towards healing the national divisions that everyone acknowledges is neither to heap sarcastic love upon our opponents, Boris Johnson-style, nor to harp constantly on about the will of the winners. The way back to any kind of consensus is to insist upon a parliamentary democracy with its rules and principles intact. This is what sovereignty means: building the rules together, not changing them unless it’s together, and playing by them together.

• Zoe Williams is a Guardian columnist