Over the weekend, the Times reported that Alex Salmond, the former First Minister of Scotland, has made an extraordinary attack on Nicola Sturgeon, his successor and one-time protégé.

In evidence to the man investigating the SNP leader’s conduct, he claims that Sturgeon has misled the Scottish Parliament and broken the ministerial code by failing to keep civil servants informed of her meetings with him over sexual misconduct allegations.

We’ve covered the affair in the Red, White, and Blue column, although this latest twist has seen another round of pieces offering the broad sweep of the story. But the nub of it is that Salmond is convinced that Sturgeon and her allies stacked an official inquiry against him in order to try and prevent his return to front-line politics in Edinburgh, and now he’s out for revenge.

This inter-personal drama is made much more dangerous for the broader party because it intersects with several other fault lines running through the Nationalists, over independence strategy, gender politics, and more besides. Just as the SNP stands on what might be the cusp of fulfilling its historic mission, its phalanx-like discipline is breaking down.

What the political fallout of all this will be is less obvious. So far, the Scottish Government has enjoyed the same sort of political un-life enjoyed by Theresa May’s administration when it was shedding Cabinet ministers left and right but still comfortably above 40 per cent in the polls. The SNP’s electoral coalition is held together by an existential constitutional question and seems fairly impervious to day-to-day misgovernment.

But if Salmond’s allegations against Sturgeon are substantiated – a big if – that could be a problem of a different order. The First Minister would probably have to resign, and even if she toughed it out her reputation would be severely damaged. The damage to the broader Nationalist cause could be severe because, as research from These Islands has illustrated, the extraordinary esteem in which she is held by Scottish voters is one of the biggest assets they have.

The Nationalists took office in 2007, and since then unionists have not succeeded in building a political machine to match them. It would be a strange twist of fate if the thing to deliver the Union from the SNP was the SNP itself.