In her nearly four years as leader of the Scottish Conservatives, Ruth Davidson’s star has experienced a seemingly continuous ascent. Her grit and her personality have both won her many Tory fans on both sides of the border – not least because of her willingness to champion conservatism in the teeth of the Nationalist gale, and her appreciation that modern politics rewards authenticity and humanity (has any other frontline politician shared their celebration of a £40 scratch card win with the nation?).

With Labour still in crisis in Scotland, and the SNP inevitably demanding another instalment in the Neverendum, the opportunities and responsibilities of her role continue to grow. On past performance, her star will rise further still under such pressures.

So it’s notable – and, I confess, a little concerning – that she has today delivered a speech about her intention to vote to remain in the EU.

When I say that it’s concerning, I don’t for a minute mean to imply any negative reflection on her. Unlike some others who will campaign in favour of EU membership, Davidson is a democrat who has always supported an EU referendum; she is a fair leader who has given her MSPs a free vote in the ballot itself and supports CCHQ resource neutrality; and her speech is explicitly about a practical case for Remaining, based on her personal “cost benefit analysis”, rather than the starry-eyed delusions that the europhiles of the world exhibit about this flawed project. Her assessment centres on her opinion of the economics of EU membership – I certainly disagree with her on that opinion, but it’s an honestly held one to which she is entitled.

Instead, my Outist’s concern at her announcement arises from two factors. First, Davidson is an undoubted asset to her side of the debate. The Remain camp is largely populated by tired Blairites, now driven from their natural habitat by Corbynite hordes, fringe obsessives who are unwilling to brook any criticism of their beloved project and discredited Jeremiahs, who wrongly predicted disaster if we failed to join the Euro. The addition of someone who is none of those things, and instead is an optimistic politician who has a feel of the modern world about her, is undoubtedly of benefit to that cause.

Second, her speech illustrates what looks likely to be the most stark dividing line on the EU question within the Conservative Party. It isn’t between generations, between genders or even particularly between sects of the Party – instead, I suspect it will prove to be whether you are a Scottish Conservative or not. Davidson’s speech focuses on the economic aspects: particularly on questions of trade with the EU and the concept of EU trade deals with other parts of the world. But in the back of many Scottish Tories’ minds is the impact a Brexit might have on the SNP, and thus on the Union.

Opportunists that they are, Sturgeon and Salmond will reliably seek out any excuse to demand a new independence referendum. Their current wheeze is to insist that Scotland should get a veto on the United Kingdom’s decision in the EU referendum. This of course misses the point that Scotland just voted to stay in a Union, but it’s a point that’s missed deliberately. Having breathed a sigh of relief at saving the Union a year ago, it’s fair to say some Scottish Conservatives are getting nervous about the idea that a vote to Leave the EU could open the door to a new Scottish independence vote.

Furthermore, the SNP’s leaders know that the Brexit argument can be twisted to offer them the chance to make Unionist Eurosceptics uncomfortable. As I warned in February 2014, the willingness of some in Better Together to reach for apocalyptic language about Scottish independence – the fears of being alone in a hostile world and thus doomed – were a gift to those who intend to make the same warnings about leaving the EU. The two Unions are utterly different (one is functional, productive, democratic and culturally coherent, while the other is the very opposite) but soundbites blurring them together will be easy to manufacture nonetheless. If the Nationalists manage to equate leaving the EU with leaving the UK, then plenty of Scottish Unionists could well decide, albeit grudgingly, to accept the blue and yellow flag in the belief that doing so would preserve the red, white and blue one.

Tellingly, it is in that context that Davidson concludes her speech:

“I believe – and campaigned for – Scotland to stay part of a wider Union. And I believe Britain should stay part of a wider Union, too.”

No-one – including CCHQ itself – yet knows how the Remain/Leave numbers stand among Scottish Tories. ConservativeHome’s national surveys of Party members suggest that almost 60 per cent would vote to leave the EU. Anecdotally, many in the Scottish Party expect that number to be dramatically lower – and even possibly reversed – among members there. The tide of Nationalism is battering at the infrastructure and landscape of Scottish politics, and it is bending each out of shape. Ruth Davidson’s intervention is a product of her personal beliefs, but also of the tilting, twisting battlefield on which she now stands.