At a public discussion about Brexit and devolution in London in March, I asked the Scottish National Party MP Philippa Whitford what she thought the consequences would be for Scotland. “I’m in no doubt there will be a referendum [on independence] again in the next two years,” she said.

It wasn’t much of a question, and “Top Scot Nat predicts indyref2” isn’t much of a headline, but nevertheless I was taken aback by her expression of total certainty. As far as I’m aware, not even Nicola Sturgeon is as sure as all that.

But then, for those of us who are not part of the SNP’s inner sanctum, the strategising and calculation taking place within it are a thing of mystery and wonder. If you’re not a Nat, it’s quite hard to think like one. Where, for example, does the balance lie between governing well in devolved Scotland and doing everything possible to advance the case for independence? After all, the two are not always in accord. Are the Nats determined to have a second vote on separation soon, regardless of the polls, or are they willing to play a longer game?

Whitford is no fool – a distinguished breast surgeon, she is smart and savvy and across the detail of policy. But what, then, to make of this week’s utterance from her normally gung-ho Westminster colleague Pete Wishart? The latter is neither a surgeon nor, it feels uncontroversial to say, particularly smart or savvy, but he somehow seems to have detected a change in the wind.

In an article for iScot, one of those odd little pro-independence newsletters consumed only by diehards and MI5, he struck a cautious tone in relation to a new vote. “There is only one thing that determines my approach to a second independence referendum and that is winning it. Losing again is simply unthinkable and we have to ensure that we are as pragmatic as possible in ensuring that next time we get over the line... we must ensure that it is held under the optimum conditions for success.” While it was “possible” that an early vote could be called, “holding a second referendum only to lose it because the Scottish people weren’t ready would be the worst possible national tragedy. Holding [one] and losing when we could have won if we were just a bit more pragmatic about the timing would be even worse than that.”

Setting aside Wishart’s amusing lack of perspective – “the worst possible national tragedy” – this felt like a significant intervention. Its author has been an active online troll of Unionists, which has made him a favourite of the Nat ultras and a figure of some contempt among pro-UK voters. Given the messenger, and the chosen audience, it therefore seems like a message is being sent.

It might have something to do with a pro-independence march that is due to take place on 5 May in Glasgow. Its organisers claim 7,000 people took part last year and they hope to double that amount, and bring the city to a “standstill”. The SNP membership numbers remain swollen by the newbies who joined after the 2014 referendum defeat. Newly politicised and with little of the strategic patience shown by the old guard, they want another vote and they want one now. Managing this pressure, and avoiding disillusionment, is one of Sturgeon’s biggest challenges.

The First Minister had her fingers burned after the Brexit vote. With Scotland voting Remain by a 62-38 margin, she said there had been a “material change” of circumstances since 2014, and that she intended to hold a second referendum. There was little voter appetite for a rerun so soon, and the SNP subsequently lost 21 of its 56 MPs in the 2017 general election.

While cooling her rhetoric, Sturgeon has kept her options open, most recently saying she will decide in the autumn whether she wants to pursue another referendum, based on the details of the Brexit deal.

There are plenty barriers in her way – not just the current lack of interest among the electorate, but the fact that Theresa May has said she will not sanction another vote. That would leave the SNP having to opt for a Catalonia-style rogue poll, creating a constitutional crisis, undermining the validity of the vote, and risking Unionist fury. Set against this, the polls suggest the next devolved election in 2021 will produce a pro-Union majority. Time is running out.

None of which is to say the climate can’t change. When it comes to Brexit, as Whitford put it to me, many Scots feel like “we’re not in the back seat of Theresa’s car, we’re in the boot”. And, as she also said, there are undoubtedly voters who backed Remain in 2016, and voted against independence in 2014, who now feel “the UK I voted to remain part of doesn’t exist”. I’m not immune to that sentiment myself. But the emotional and intellectual leap to backing the final break-up of Britain remains a considerable one.