Andy Maciver is Director of Message Matters and a former Head of Communications for the Scottish Conservatives.

A new movie hit theatres late on Thursday. Landslide 2: The return of Maggie Simpson, follows on from the 2015 original, when Britain’s electoral map first bore a striking resemblance to the cartoon character. Having abandoned their plans for a sequel in 2017, the nationalist directors of the franchise, although not quite perfecting the shade of yellow on Maggie’s face, have benefited from stronger performances from the blue actors in the south to create the starkest difference we have yet seen.

Away from the movies, we hear cries of ‘constitutional crisis’. I tend to find this slightly exaggerated, but what is certainly true is that we are at a constitutional crossroads once again.

A decade ago, the protagonists were Alex Salmond and David Cameron. Readers of this website may not like to admit it, but the truth is that Salmond came out on top of that contest. Scotland may have voted No in 2014, but it did so narrowly and after a calamitous campaign, led by Downing Street on the advice of past-it peers and people who only went to Scotland on day-trips, which through its unthinking adherence to the constitutional status quo pushed people into the waiting arms of the nationalists. They have never come back.

Boris Johnson does not have the luxury that Cameron enjoyed; he won’t get a second chance to get Scotland right. If there is another referendum, it’ll be the last one, and it will happen on Johnson’s watch. He will now, almost certainly, be the Prime Minister who will either lose Scotland, or kill nationalism.

How does he ensure that he achieves the latter outcome?

He must understand and accept three fundamentals.

The first is that he can’t be a fair-weather democrat. He should be able to relate to this, easily, through his experience of Brexit. His victory last Thursday means he will now implement the democratic will of the people, by leaving the EU. The winners will win, and the losers will lose – that’s democracy.

We can hold a mirror up to respecting Brexit and see in it respecting Indyref 2. To do this we must ignore the hysterical wailing from some in the Scottish Tory Party who have perfected contortionism in their attempt to claim that perpetually denying another referendum is the democratic outcome.

The SNP’s current mandate is vague, and the strongest iteration of it, in my view, comes from June 2016, when the UK’s Brexit vote fulfilled the SNP’s winning manifesto criteria from the month before (Scotland being taken out of the EU against its will). Last Thursday’s mandate is far weaker for a variety of reasons, primarily that some now-MPs pulled ‘loaned’ votes by making clear that it was not a vote for Indyref 2, and because the SNP’s primary platform was to stop Brexit.

But none of these arguments will pass muster if the SNP wins the 2021 Scottish Parliament election – the most important there has ever been – with a clear and unqualified manifesto commitment for a second independence referendum.

You can’t demand to get Brexit done because voters asked for it whilst demanding that Indyref 2 be continually rejected despite voters asking for it.

The second way to ensure a better outcome is to understand that the current Scottish Tory position – vote for us and we will stop Indyref 2 – is a vote-losing, party-killing, Union-ending continuation of the same Scottish strategy the Party has had for 40 years.

The Conservative Party has never, ever, been ahead of the curve on Scotland. It has been in permanent reactive mode: oppose devolution and then support it after it’s already happened; create the Calman Commission to appease the nationalists after they win in 2011; create the Smith Commission to appease them after they almost win in 2014.

Since then, its ‘no to Indyref 2’ strategy – designed to expand its support by encouraging Labour unionists to lend their vote to the Tories – has ridden the crest of the wave and at times propelled them to almost 30 per cent in the polls. But those in the bubble need to understand that on Thursday night the bubble burst. The strategy failed; it now amounts to a core-vote strategy because the ultra-Unionist vote has probably been maximised.

The Scottish Tories now need to change their position to one which is more credible, more democratic, and has a better chance of success in 2021, and if up here they can’t see the wood for the trees, Johnson should change it for them.

Their position has been ‘vote for us and we will stop Indyref 2’. They should alter it ahead of 2021 to ‘vote for us or we will not be able to stop Indyref 2’. In other words, the Party should acknowledge that a mandate in 2021 will have to be respected, and there will have to be another independence referendum, so if you don’t want one then you had better vote Tory.

This is just as compelling for the core vote, but the respect it would show for Scottish democracy would also extract the maximum number of Labour and Lib Dem voters who would be prepared to coalesce around the strongest unionist voice.

Johnson would likely find common ground with Nicola Sturgeon on this. It is often misunderstood by the London media that Sturgeon is currently calling for something she doesn’t want (a referendum in 2020) and getting in response something she does want (a grievance-stoking ‘No’). It is an open secret up here that she and her advisers are worried that, despite Boris and Brexit being their perfect storm, the pro-independence numbers are too weak to be confident of success in 2020. They want more time. They need more time. Johnson could give them more time by setting them the test of winning in 2021, whilst also damaging the grievance agenda.

This is where the third fundamental becomes relevant. The Tory Party has now spent so many years obsessing about Indyref 2 that it seems to have lost all confidence that it can actually win the damn thing. With that, the message it is sending is that it has lost all confidence in the Union as a winning force.

There is no question that there are some strong fundamentals in place for nationalists – demographics being the most obvious one.

But unionists need to stop being so negative and paranoid about their own upsides. There are three significant ones. First, Scotland is constitutionally fatigued, and by the time Brexit has settled will be both weary and wary of more change.

Second, the SNP’s position on rejoining the EU could easily become toxic when we start discussing a customs border at Gretna.

Finally, if Johnson’s government avoids the mistakes of Cameron’s, and runs a campaign based on a strategic vision of what devolution will look like in the much longer-term, he will give Scottish people what they have always wanted but have never been offered – the ‘something in the middle’ option.

Boris Johnson will go down as the Prime Minister who lost Scotland. Or he will go down as the Prime Minister who ‘won big’ on the two biggest constitutional conundrums of the century. There’s nothing in between, anymore.