The secret to Vote Leave’s success was not illegality but ambiguity. While it is true, as the Electoral Commission has now ruled, that the official Leave campaign broke electoral law by overspending, its greatest political trick was managing to offer a welter of contradictory futures wrapped up into a single idea: Brexit.

Vote Leave promised to spend the whole of the United Kingdom’s net contribution to the EU budget on the NHS (that famous £350m a week) while pledging to extend the subsidies handed to farmers and scientists. It offered an end to the free movement of people and a de facto reduction in immigration while laying out a future in which the UK struck trade deals with India and Brazil, both of which would require more visas for their citizens in return for greater access to their markets. It promised parliament the freedom to set British laws without regard for anyone else, an impossibility in the era of globalisation. It held out the notion of leaving the customs union while keeping the border with Ireland as open and invisible as it is now. Almost 17-and-a-half million people voted Leave – and you could argue they each voted for a different kind of Brexit.

The Conservatives’ big problem is that they can only deliver one version – and whatever it is, it will inevitably be greeted as a betrayal by at least some voters. Worse, the flavour of Brexit that is most popular with Conservative MPs – deregulation, untrammelled free trade, open markets – has no significant following in the country.

Theresa May aggravated the problem by using her first speeches to raise, rather than lower, expectations. Voters have now largely tuned out of the Brexit debate. During a recent BritainThinks focus group in Watford, I heard one Leave voter liken the process to the final stages of a divorce – the lawyers were wrapping up the whole sorry business and it was now just a matter of waiting for the payout on both sides.

That pattern has also been observed in the focus groups conducted by Conservative strategists. These tell the same story: of ordinary people switching off from the Brexit conversation, of sky-high expectations for the final deal, and most troublingly for the Tories, of a party brand that is now irretrievably associated with Brexit.

If Brexit goes well, the Conservatives will get the credit; but a bad deal will see them shoulder the blame – even with a new leader. Recovery from trashing May’s deal would not be the work of months, but of whole terms in opposition. That is part of the calculation that has kept Michael Gove and others in the cabinet and it is why Brexiteers are badly split on whether or not to oppose the Chequers compromise.

Yet the difficult truth is that the Brexit process has not entered its final stages; the lawyers are very far from dotting the i’s and crossing the t’s; and the payout is likely to be non-existent. In fact, the Office for Budgetary Responsibility has estimated that Brexit will hurt the public finances, reducing the tax take by 1.5 per cent every year.

And while a minority voted believing that getting poorer was a price worth paying for greater sovereignty, a majority did not. That’s why many Conservative MPs still refuse even to acknowledge that the trade-off exists. This means that, when detailed Brexit questions come to the House of Commons, Tory rebellions are inevitable. To pass any deal, May will need votes from somewhere else.

They won’t come from the Labour leadership, though, who feel increasingly confident of winning the next election. The question being asked in the leader’s office is whether the Chequers plan, and subsequent bloodletting, will breach the Conservatives’ “purple firewall” of former Ukip voters who are boosting the government’s support. (At the general election last year and the local elections in May of this year, the Conservative vote share was kept robust, and a Labour victory seen off, thanks to the votes of ex-Kippers.) Labour strategists are now testing what messages most effectively peel off Leave supporters from the Tory pile. Contenders include promises on public ownership of the utilities – an idea that polls particularly well with Leave voters – and a simple “betrayal narrative” about whatever deal May strikes.

A greater appeal to grass-roots Brexiteers might explain why Labour has re-established a lead in the polls for the first time since the spring. It might pay even greater dividends at the next election, but it also stymies Labour in the present. The opposition cannot vote for May’s final deal if it hopes to get to Downing Street on the back of popular discontent with the plan. Added to that, the expectation – shared even by the leadership’s most committed Eurosceptics – is that her deal will be both half-baked and damaging to the economy, which means there is no incentive for Labour, either electorally or politically, to support it.

Where can May go from here? She has no good options. She cannot soften the deal enough to convince Labour’s most committed pro-Europeans, the Liberal Democrats or the Green Party to lend her the necessary votes without ripping her own party in two. As for the Scottish National Party, as one close observer of First Minister Nicola Sturgeon notes, it is difficult for her to countenance voting with the Tories under any circumstances.

After all the talk of a “meaningful vote”, we have ended up with a parliament that can only say no. Tory Brexiteers will reject anything that contradicts their wildly incompatible promises before the 2016 referendum, while the one thing Labour will be able to unite behind is that May’s deal isn’t good enough – whatever it is.

This, then, is the inevitable result of a referendum in which the promised destination was always illusory.