Andy Maciver is Director of Message Matters, and a former Scottish Conservative Head of Communications.

Ruth Davidson’s back. A sprightly interview with the BBC on Monday laid the foundation for the territory she wants to occupy over the next two years until the 2021 elections to the Scottish Parliament – a second Scottish independence referendum.

Her line on it – that the people don’t want one and I’m the people’s human shield to stop it – is tried, tested and successful. She is the undisputed Queen of the Union, and her iron grip on that throne at the expense of Labour is what doubled her representation at Holyrood in 2016, and delivered the 13 MPs in 2017, without whom Theresa May would not have re-entered Downing Street.

Whether her “not now, not ever” line will hold if the SNP gets a newer, stronger mandate in 2021 (spoiler alert – the line won’t hold), and whether it’s good medium- to long-term strategy for the Tories to be the party which continually says no to Scotland’s democratically elected government (spoiler alert – it’s not) is for another article.

For this piece is not about the issue that Davidson does want to discuss – namely, independence. It’s about the issue she doesn’t – Brexit – and the severe consequences it brings for the Scottish party.

The principle of Brexit has proven to be less of a problem for the Scottish party than some had thought it would. For sure, Scotland is a Remain country, but 38 per cent (the Leave vote) is a million people for the Tories to target, and polling both for independence and for voting intention remained largely unchanged until recently.  Indeed, a stronger, coordinated push by the 13 Conservative MPs for an EFTA/EEA outcome could have been a rocket-boost for Tory fortunes north of the Border.

But, even as it is, the principle of Brexit is manageable. However, Davidson returned this week to mounting evidence that the practical consequences of Brexit are not. There are three such consequences.

First, it is entirely possible that the Scottish Tories will lose the single Scottish MEP seat they currently hold in the coming European elections. So what would that matter, right: after all, MEPS will only be in a job for a few months and nobody pays any attention to them anyway? Sure – but getting people out of the habit of voting Tory, when they’ve just started to get back into it, is a momentum-killer.

Second, whilst Scottish Conservative polling had held relatively firm in the mid- to high-20s for around three years, it has now taken a decisive dip, mirroring the drop in UK-wide Tory polling since the Prime Minister announced the long Brexit delay. The latest poll – YouGov had them at 20 per cent last week – was bordering on a return to the pre-2014 norm.

But those consequences are the undercard to the showstopping main event, featuring Boris Johnson. When Davidson went on maternity leave in the autumn, Johnson was approaching busted-flush status, with a low expectation of him making it to the final two in any leadership contest. But she returns amidst the failure to deliver Brexit, and the perceived need to tackle the re-birth of Nigel Farage, which have propelled Johnson to the status of favourite once again.

Readers may recall a series of briefings last year code-named “Operation Arse” – this was the Scottish Tory-led ‘Stop Boris’ campaign. It was widely known that this was based on a combination of internal polling and Davidson’s own disdain for Johnson.  That polling was never released: however, I understand the numbers to have been so severe that they incited jaw-dropping astonishment and effectively put the Scottish party on a crisis management footing.

Johnson was shown to be unpopular across all Tory voters – the core, 2016 switchers and 2017 switchers. He was the least popular of all leadership candidates. His favourability, I understand, was around -40. May, at the time (although it will inevitably have dipped) was +40, and Davidson +80.  He was as unpopular in Scotland as Jeremy Corbyn.

The backdrop to this was the party’s polling and focus group evidence telling them that they had a chance of being the largest party in 2021 (I have never thought this is achievable but that is hardly the point).  Those Johnson numbers are not just acting as a bump in the road towards this outcome; they point to an end to that road.

This is why, as the Scottish party heads into its spring conference this weekend, talk of separating the Scottish party from the UK party is firmly back on the agenda. This proposal came to prominence in 2011, when Murdo Fraser’s leadership campaign was based on the platform of creating a new party (full disclosure – I helped).

As far as I’m aware, none of its original supporters (let’s call them the 2011 Team) have changed their minds. One can see why. Ruth Davidson is Scotland’s most popular leader, persistently out-polling Nicola Sturgeon over the last couple of years, and just last week recording a net positive rating of +10 compared to the First Minister’s +1 and the Prime Minister’s -58.

And yet, despite that, the First Minister’s party remains soaring at over 40 per cent, with Ruth Davidson’s unable to even reach its fingertips to a number starting with a 3, and now ostensibly struggling to hold on to a number starting with a 2. Does nobody ask why? Does nobody ask what is stopping people voting for the person they like the most?

Outside the bunker, the answer is slapping us across the face, and no more so than this week as we see, yet again, the harsh winds from London blowing the Scottish polling off course. ‘Twas ever thus. The 2011 Team knows that this will ebb and flow, but it will never fundamentally change. The ties are too strong.

But the 2011 Team are no longer the only advocates of a separate party. They have been joined by, let’s call them, the 2019 Team. These are people who are unsupportive of the principle of a separate party, but believe that it may be the only practical way to stop what they regard as a catastrophic, perhaps existential threat posed to the Scottish party by a Boris Johnson leadership.

The reticence in some quarters, not least in London in 2011, when the establishment moved mountains to prevent Fraser winning, is a puzzle. With hindsight, I think those of us involved with Fraser in 2011 must take some of the blame. The slogan was “A new party for Scotland” and, whilst that was the right message for the country, it was a frightening message for the party membership.

It was the right product, in the wrong packaging. Instead, we should have looked to the past rather than the future (we did mention it, but it wasn’t the central plank). Because the reality is that what Fraser was arguing for was a return to the pre-1965 structure, when the Scottish party was separate (and more successful).

In truth, the centralisation of the party from 1965 until now should be seen as a historical blip; as an experiment gone wrong. This would not be a leap in the dark. It would be a return to the party’s roots.

This idea returns, from time to time, because it contains an inevitability. It will never die. It will happen, because it is so blindingly obvious that it should. Scotland created a new parliament and a new voting system and dumped the old party structure on it, with a sprinkle of nationalism on top. It had no right to work, and it hasn’t. The pro-union parties are structurally unable to adapt to changes in public opinion and are forced into the negative end of a binary debate.

Unionism and centralism are not the same thing. Observe Canada, our closest peer in this respect, which has provincial parties for provincial parliaments and national parties for the national parliament. And is at next-to-no risk of separation.

The centre-right can win in Scotland. But the Conservatives can’t.  As a party grandee told us when endorsing Fraser in 2011 “you’ll lose this time, but the beans will never go back in the tin”.