The history of politics tells us how things are supposed to happen. A party gets elected, there is great joy, and rejoicing, and big promises. Then, after a few years, events, entropy, and human nature start to cause problems. Politicians are caught with their hands in the till, or in something else, and the party is brought down. The timeline is usually 10 to 15 years. Look back at history. It’s what happens.

But not with the SNP. The SNP is different. Yes, the Derek Mackay scandal will have some effect on the party’s reputation. Yes, it will further corrode some of the once-shiny metal of the party machine. But I’m prepared to bet good money – I’m from Aberdeen so let’s keep it relatively small, £50 say – that when the next opinion poll is released, the Mackay affair will have made no difference to support for the SNP. None. Zero. I’m confident my 50 quid is safe.

The reason I’m confident is that, within the history of British politics, there is the history of Scottish politics and it tells us that many Scottish voters behave differently because of how some people feel about England. For decades, Labour’s support in Scotland was immune to events, including scandal, because the party was seen as pro-Scottish and anti-Tory.

Even the eventual downfall of Labour in Scotland happened for the same reasons it lasted so long – some voters started to see the SNP instead as more pro-Scottish and anti-Tory than Labour and so switched sides. And the votes for the SNP came with the same guarantee: stay “pro-Scottish” and anti-Tory and you’ve got our support come what may. Scandals? Who cares!

READ MORE: Analysis: Does Derek Mackay scandal mark the beginning of the end for the SNP? 

Just so you know, I’m not saying this unswerving loyalty to the SNP will last forever – even winter in Narnia came to an end eventually – but it will last way beyond the usual cycle of success followed by crisis followed by defeat, and it will remain immune to scandals such as the Mackay affair for a good while yet. Breaking the SNP loyalists down into several categories explains why.

The first category is the most unpleasant: the apologists, who we first encountered when the claims of attempted rape and sexual assault were made against Alex Salmond. Salmond was the victim of a Unionist/MI5/UK plot, they said; others said Salmond’s accusers were either lying or had “thrown themselves” at the former First Minister. There were also questions asked about why it had taken “so long” (five years) for the complaints to be made, the implication being that complaints that are not made immediately might be fake.

Sadly, two years on, we’ve seen exactly the same kind of thing with Mackay. One SNP councillor said it was all probably a honey trap set by the British establishment. There were also some who questioned the motives of the 16-year-old boy’s family in the same way they questioned the motives of the women who accused Salmond. Why did the boy’s family go to the papers rather than the police? they said. I’ll tell you why: because Mackay was a public figure and the public has a right to be told about his behaviour.

Even more worrying was the apologists’ attempts to normalise what happened. Some expressed pity or sympathy for a man who’d made a mistake; others pointed out that 16 is the age of consent and called the connections between Mackay and the boy a “relationship”. And I think I could detect a form of homophobia (at worst) or stereotyping (at best) in the attempts to portray Mackay as just your normal, partying, good-time gay guy with an eye for young men.

But the apologists do not explain everything because there’s another category of voter who will stay loyal to the SNP for different reasons. These are the voters who are appalled by Mackay’s behaviour but have nowhere else to go politically. There is one other party in Scotland that supports independence – the Greens – and some voters may drift there in the end, but if you want independence, you’re probably forced to conclude that the SNP is the only option, scandal after scandal after scandal, unless and until another major force emerges in independence politics.

The final few categories of SNP voter also explain why support for the party will hold up. Some will judge that the behaviour of one man is not as important as the policies or achievements or aims of the government. Fair enough. Others will be motivated by their dislike of the Tories. Also fair enough. And, let’s be honest, there will be some who are motivated by the oldest of Scottish diseases: Anglophobia. They will say to themselves: we hate men who abuse their position of power, but we hate the English more.

The effects of all of this on support for independence will be interesting. There were some who predicted the beginning of the end for the SNP, and even support for independence, after the Salmond accusations became public, and they make the same predictions for the trial in a few weeks’ time. But if you’re a hopeful unionist, my advice would be: calm your jets. Salmond’s travails have not affected the political balance at all – if anything, the dial has flickered a little towards the SNP and independence – and I can’t see why the Mackay scandal should be any different.

READ MORE: The messages that led to Derek Mackay's downfall 

Perhaps, in the end, this is a good thing. Tony Benn used to say that policies matter more than personalities, and maybe the debate about independence has proved him right. The Yes side has been hit by many serious scandals involving personalities like Salmond and Mackay, but every time voters are asked about independence they say it’s the economy that counts the most when making up their mind.

This matters because of what we know about the potential economic damage of independence. Voters aren’t worrying much about who an SNP minister is messaging – troubling though it is – they’re worrying about what could happen if Scotland is taken out of the UK single market. To that extent, unionists, and the undecided, care as little about the Mackay story as nationalists do. It is still a crisis for the Government, but economic consequences matter more than morality, financial affairs matter more than personal ones. The SNP may be immune to scandal for now, but in the long term, the real worry for the party, and the cause of independence, isn’t sex, it’s money.