Politics is changing so fast these days that it’s becoming hard to keep up. No sooner had the General Election changed the face of Scottish politics than UK politics was seized by Corbynmania. The no-hope left-winger is now the bookies' favourite to win the UK Labour leadership.

Every day brings another shock. Yesterday it was the Daily Record coming out for Jeremy Corbyn. Who could have expected the paper of the Labour establishment (as was) turning to the radical left? But it's not just in Labour that the times are a changing. The Corbyn surge has swept across Scottish politics, disrupting old alliances and conventional wisdoms.

It used to be that there were two tribes in Scotland: the SNP and Labour, who hated the ground each other stood on. They still do, but there is a deal of fraternisation in no-man’s land.

Tribalism in Scottish politics has long prevented both SNP supporters and Labour supporters admitting that they share many of the same social objectives. Now, there's an almost palpable sense of relief among some on the neo-nationalist left that they can say something nice about Labour for a change. Politics is no longer just about the binary Yes/No of the constitutional debate.

Indeed, there appear to be three tribes in Scottish politics: Nationalists, Labour and Corbynites. Their supporters wander promiscuously along the battle lines drawn up during the 2012-14 independence referendum campaign.

On social media, where so much of Scottish politics takes place, Yes voters who have been intensely critical of the “Red Tories” are finding themselves themselves suddenly applauding the man most likely to be the Red Tories’ next UK leader.

The Corbyn surge, though, has caused turmoil in Scottish Labour ranks. The former Scottish Labour MP, Tom Harris, and the former Scottish Labour leadership candidate, Neil Findlay, had a sharp exchange on Twitter yesterday. Mr Harris, who supports Liz Kendall, accused Mr Findlay, who supports Corbyn, of dealing in “Trot abuse” (he later apologised).

For their part, the SNP have largely welcomed the Corbyn phenomenon, even though Ms Corbyn is a Unionist who opposes another referendum and new powers for Holyrood. They can't help sympathising with a politician who not only shares many of their left-wing views but has also been attacked by Better Together’s former chairman, Alistair Darling, and the Conservative press.

There is also a striking overlap of policy, independence aside, between the SNP and Mr Corbyn. In fact, there is a plausible case to be made that the Corbyn phenomenon actually began with Nicola Sturgeon’s appearances in the televised leadership debates during the 2015 General Election campaign.

It was the SNP leader’s spirited advocacy of social democratic themes including unilateral nuclear disarmament, wealth taxes and public investment that ignited interest among disaffected Labour voters. "Why can’t we vote SNP too?" they asked. In a Herald/TNS opinion poll in April, Ms Sturgeon was the most popular political leader, not just in Scotland but in the entire UK.

However, Mr Corbyn's success poses a potentially serious challenge to her brand of civic nationalism. She has always said that, for her, independence is not an end in itself. She describes herself as a “utilitarian” nationalist, not an “existential” one. She means that she sees self government for Scotland as a route to social justice, not a celebration of ethnic or racial exceptionalism.

Many of the new SNP MPs are firmly of the utilitarian tendency. The former Labour activist, Tommy Sheppard, SNP MP for Edinburgh East, says he isn’t even a nationalist, at least not in the conventional sense. He is as committed to social democracy as when he was in the Labour Party.

Many on the Yes side of the independence debate are of a similar view. It was Tony Blair, the Iraq war, tuition fees and privatisation that turned so many Scots against Labour and made independence seem the only route to social democracy. A Corbyn victory could lead to a drift away from the SNP and back to a UK-wide socialist project.

Labour's membership has been exploding in much the same way as the SNP’s after September 2014, though it’s unclear how many of the 250,000 new supporters are in Scotland. But if this continues, it could alter the dynamics of Scottish politics.

Mr Corbyn has moderated his hostility to nationalism recently but he is still a Unionist at heart. He has talked of cooperation with the SNP, perhaps in some form of post-election pact.The Islington MP avoided all talk of the SNP when he visited Scotland last week but there is no reason to suppose he has become at all sympathetic to independence.

He has talked loosely about a possibly federal future, but there is no suggestion from him so far that he has a fully worked-out plan for reforming the UK constitution along federal lines. The constitutional issue, as he says himself, is really of very little interest to him as a “socialist”.

This is both good and bad for the SNP. Good as the SNP retains a monopoly on the Scottish dimension, identity politics and the constitutional issues that have dominated Scottish elections in recent years. Bad as the Nationalists might start losing the weaker independence supporters who might become attracted by a vision of a socialist UK.

It's too early to say how these factors may play out, mainly because we do not know if Mr Corbyn will be a credible leader even assuming he wins. The Labour right have put a contract out on him; people are trying to smear him (disgracefully) as an anti-semite; the press will round on him and he may be in office only a matter of months.

If there is a nasty, right wing counter-coup against Mr Corbyn, support for the SNP could boom as Scots give up on any lingering hope that the UK can be reformed. This is certainly the view of some Unionists such as the Spectator blogger Alex Massie.

There is also the Sturgeon factor to take into account. Left wingers would love to believe that the SNP triumph in May was all about social justice and wealth taxes, but it also had a great deal to do with the personality of the SNP leader. Voters are besotted with her. Ms Sturgeon seems to represent everything that Scots, especially younger Scots, want to see in themselves: smart, clever, modern, unapologetically Scottish.

A 66-year-old bearded London intellectual is always gong to struggle when pitched against the most formidable political personality in Scotland, if not the UK. She can also claim the credit for having placed left-wing ideas such as unilateralism back on the UK agenda before Mr Corbyn was even a candidate.

So, on balance, I would say that Mr Corbyn is not going to seriously alter the balance of power in Scotland, especially since Kezia Dugdale, the new Scottish leader, seems to have largely stuck to Jim Murphy’s pre-Corbyn cabinet. But the SNP could find they will have to work much harder to establish their left-wing credentials in future. Ms Sturgeon is no longer the only pin up for Scottish social democrats to put on their bedroom wall.