Now we know how Theresa May plans to sell her Brexit deal, we're closer than ever to an agreement

The prime minister may deny that hers is a ‘blind Brexit’, but it will certainly be a vague, all-things-to-all-people declaration

Stand by for the hard sell of Theresa May’s Brexit deal. True, there isn’t an agreement yet. Sources in Brussels tell me that the EU will not be bounced into accepting May’s latest proposal on how to avoid a hard border in Ireland.

But the prime minister made significant progress on Tuesday in persuading her cabinet to swallow its doubts about her plan. She is using the rising prospect of a chaotic no-deal scenario next March to pressurise her ministers and the EU to support her blueprint.

May will do the same when she faces her biggest Brexit hurdle: selling her deal to parliament, which has to approve it. A leaked document provides an insight into the government’s thinking. “Historic moment, put your own interests aside, put the country’s interest first and back this deal,” it said, in a section on the critical Commons vote. Downing Street dismissed the leak, insisting this is not the government’s communications plan – but it didn’t do a Donald Trump and claim that it was fake.

My guess is that it was written by a junior official; five names listed as possible endorsers of the deal, including that of the Irish prime minister, were spelt wrongly. It was probably leaked by someone who doesn’t think that May’s deal will be a real Brexit, despite the plan for her to make a speech saying “we have delivered on the referendum”.

The document, from the Department for Exiting the EU (DExEU), was based on the cabinet signing off May’s agreement on Tuesday. In fact, another meeting will be needed, possibly later this week. Listing 27 November for the crucial Commons vote was naive, since the EU’s timetable will almost certainly require the political declaration on future UK-EU relations to be approved at its summit on 13-14 December.

I rather doubt that Dominic Raab, the Brexit secretary, will be the one to trumpet the crucial breakthrough, as the memo said. After enduring so much pain, surely May herself will be in the driving seat.

However, the approach set out in the document rang true. May will present her agreement as in the national interest; this deal is as good as it gets – and, in other words, no one else could get a better one.

It will suit the EU27 to say the same. They will be keen to put the messy, distracting Brexit process behind them, for a while at least.

Although the leaked report insisted the big sell will be about “measured success” rather than “champagne corks popping,” May will enjoy the taste of a crucial ingredient – momentum – once she gets her deal. Business will breathe a huge sigh of relief, not because it will be a great deal but because companies will have a “status quo” transitional period rather than chaos next March. It will be welcomed on the financial markets too. As one cabinet loyalist told me, the hope is that this creates a “virtuous circle” for May, which increases the pressure on MPs to support rather than wreck the deal.

Ministers know they will almost certainly need the votes of some Labour MPs to win the crunch Commons vote. But Tory whips calculate that only about 15 Labour backbenchers might buy the “national interest” argument, which might not be enough. The vote is on a proverbial knife edge.

It suits May to keep the spotlight on the important but arcane small print of the Irish backstop, the final piece of the withdrawal agreement jigsaw. Significantly, we learned on Tuesday that the declaration on the future relationship will come after the withdrawal agreement. This has the makings of another last-minute bounce just before the critical Commons vote.

MPs must put the statement about the future under the microscope. Although May will deny it is a “blind Brexit”, I suspect it will be a vague, all-things-to-all-people declaration about a “future economic partnership” and the EU’s “most ambitious free trade agreement ever”. This lowest common denominator approach is designed to allow Eurosceptics to think the UK will eventually have an EU-Canada style trade deal, and pro-EU MPs to believe the proposed temporary customs union will last a long time – perhaps forever. Probably May judges that such contradictory signals offer her her only chance of scraping together a Commons majority.

The sell will be hard in every sense of the word. Pro-EU Tories as well as Brexiteers should reject a deal that includes a woolly political declaration. The danger is that the transition is, as the appropriately-named former Brexit minister George Bridges warned, “a bridge to nowhere”.

Crucially, once the UK has signed its £39bn divorce cheque as part of the withdrawal agreement, it will have little leverage in the trade talks starting next year. No wonder the leaked document said the cabinet office’s “explainer” of the deal for the public would compare it to “no deal, but not to our current deal”.