You have to feel a bit sorry for Scotland’s Place in Europe. Delivered just before Christmas, Nicola Sturgeon’s 62-page blueprint for keeping Scotland in the EU single market after a hard Brexit seems to be one of the least read, least loved tomes of our age. It certainly seems to have received an underwhelming reception in Whitehall, where officials subjected it to a “line by line analysis”, according to Scottish Secretary David Mundell, and were deeply unmoved.

In her speech on the UK’s Brexit objectives on Tuesday, Theresa May insisted she wanted to hear what Edinburgh was saying, but by then it was essentially too late. The symbolism of issuing a 12-point plan 48 hours before the first government-to-government meeting to discuss Ms Sturgeon’s proposal said it all. A “differentiated deal” for Scotland was not one of the 12 points, and there are no plans to tack on a 13th. As hints go, it was pretty unmissable.

For those who did the hard thinking behind Scotland’s Place in Europe it’s very frustrating. The former diplomat Lord Kerr, who wrote Article 50 and now sits on the First Minister’s standing council on Europe, said it was a “rather impressive” piece of work, adding Mrs May “could have been a bit more tactful”. One of those close to the document told me they had “sweated blood” on it, and believed it ought to be treated very seriously indeed.

However there is a credibility problem for Ms Sturgeon and her plan. Many people don’t believe it. They think it’s a ploy by the SNP leadership which is designed to fail in order to precipitate another referendum. Ms Sturgeon emphatically says otherwise. However the trouble for her is that many of these people are in her own party.

One senior member of the SNP told me a lot of members saw the proposal as simply a device. Not really a serious attempt to secure Scotland membership of the European Economic Area like Norway, but a nod-and-a-wink part of the constant drive for independence. “It’s not a bloody tactic,” said my exasperated source. “It’s something that could really work.” But if Ms Sturgeon can’t get it taken seriously inside the SNP, what chance does she have of getting it taken seriously in Whitehall? Seriously enough, remember, for the UK |Government to rewrite its plans for the Article 50 negotiations to include a side-deal for Scotland.

Where does that leave her? Her predecessor Alex Salmond called single market membership a “red line” for the First Minister. She has not said that herself, but she has put so much store in the single market she may as well have. Without it, and having threatened to put the issue to the people, there seems nowhere to turn but the polls. She has ruled out a referendum in 2017, but could still call one this year and set a date. Mr Salmond suggests autumn 2018.

But it is extraordinarily difficult for Ms Sturgeon to call a referendum for next year. The polls are one element, although if 2016 tell us anything, it’s that there are no sure bets in politics. Support for Yes at 45 per cent doesn’t guarantee victory, but nor would 55 per cent. The same applies to the Unionist cause. More worrying for Ms Sturgeon is the lack of a new prospectus for independence – and how to explain the need for one.

In 2014, she and Mr Salmond said the White Paper was the definitive case for leaving the UK. Now, not only does she have to revise the economic and currency elements, she has to say why they were wrong last time, and their replacements are right. Some of this will be drowned out by Brexit, but Ms Sturgeon needs sharp answers when the time comes. Credibility again.

But planning is not enough. The coming year is impossible to game out. No plan can anticipate how conditions for a referendum will be coloured by Brexit talks, elections in France, Germany and the Netherlands, or factions in the Tories, Labour and even the SNP, not to mention Presidents Trump and Putin. Politics is increasingly reactive, about respond to quick moving events. For Ms Sturgeon, a cautious fan of the longer game, this is not natural turf. It’s also what grinds governments down, exhausting ministers and staff. Mistakes beget mistakes.

Right now, Westminster seems to sense Ms Sturgeon is on the back foot. It will want to keep her there, stalling any momentum that could help her hold and win a referendum. The First Minister has warned of a Brexit “cliff edge”. She right. She’s standing on it.