At first glance, they seem just like us.
The new left-wingers with a different colour of rosette.
They say a lot of the same things as we do. They claim to be "anti-austerity". They are against costly and increasingly pointless nuclear weapons. They opposed foreign invasions when all others seemed hellbent on spilling blood. They say nice things about equality and the rights of the oppressed. They claim representation of the disenfranchised.
Maybe my suspicion about the SNP's left-wing credentials is merely Capgras delusion, a figment of an imagination which has been let down too often by those who purport socialist viewpoints for votes.
It certainly seemed that way before the independence referendum, when much of the Left swooned at the feet of Oor Alex and Nicola.
They were our crusaders for the downtrodden Scots against the Westminster elite. They were the bold and popular progressives against the old and unpopular establishment.
Except they weren't quite what they seemed.
Call it the Invasion of the Political Body Snatchers. The SNP inhabited the body of Scotland's socialist movement, as thousands of energised activists young and old chapped doors to encourage the marginalised and angry to vote for something hopeful, something different, details to come later from our smiling new saviours.
The fervour which gripped the Left during the referendum even caused some to forget the disconnect between socialism and nationalism.
The SNP encouraged many to believe that the fate of a working class kid in Newcastle was England's problem.
But it did not take an eagle eye to see the cracks before the vote in September 2014.
When Salmond began courting Rupert Murdoch and bus tycoon Sir Brian Souter, a man not known for his progressive positions,many rationalised that it was a necessary evil to bring the business community on board.
When they unveiled a plan to cut corporation tax, it seemed a strange way to tackle inequality, but perhaps that was another essential compromise in the battle for a fairer society?
When the party made incredible claims over the post-referendum revenue from North Sea, some on the Left tied themselves in ideological knots to defend an economic argument seemingly based on the volatile and dwindling "black gold".
People were drawn to the Yes vote, and by logical extension the SNP, by a desire for radical change. The SNP were happy to bring in the idealistic left-wingers who have deserted an inert Labour Party in droves over recent years.
We can be radical after we get independence, they were soothed. But the party has now been in power for nearly a decade.
They have urged us all to think about the long game, and follow their "positive vision" for a new society but have, by any measure, been economically to the right.
The SNP's budgets have been masterpieces of deflection and mitigation. They are the party of power, the Scottish establishment, but have singularly failed to use their powers to tackle inequality north of the border.
Instead they plead democratic poverty and engineer national grievance.
Critics on the Left have been told to keep quiet and stop rocking the boat. This was the response of many Yes supporters to Loki's brilliant takedown of the SNP's meekness on inequality, and some of the excellent work by pro-independence site Common Space.
So how did we get here? To a political scene where one must extent a limb precariously above the parapet to pursue a left-wing critique of the SNP.
Because the quest for independence has become the dominant tendency in the once vibrant Scottish Left.
The SNP hoovers up progressive activists in a way the Labour Party never did, and their vaguely left-wing posturing has taken the wind from the sails of genuinely radical groups.
They have positioned independence as a uniquely left-wing concern, and in doing so have destroyed the Labour Party's claims of socialist credibility.
The pronouncement often attributed to post-war Labour minister Herbert Morrison is that "Socialism is what a Labour government does".
This mantra has been bedecked in yellow ribbons and adopted by the most ardent admirers of the Scottish Government, who now perform philosophical acrobatics to defend the SNP as they disappoint again and again with timid policy and right-wing economic pandering.
But the SNP courted the activist class to deliver the dream of independence. They promised the world, but have been scant on delivery.
The council tax freeze is right-wing populism straight out of the Osborne playbook. Swinney and co banked on the public and media being too enthralled by a middle-class electoral bribe to overlook the swingeing cuts being handed down to local councils.
Nor is hobnobbing with anti-homosexuality campaigners the behaviour of a left-wing bastion.
And calling for tax cuts on an oil industry dominated by corporate multinationals is right-wing economics in its Platonic form.
Labour's precarious position has been endlessly analysed, with many coming to the conclusion that their pre-referendum dalliance with the Conservatives was fatal.
But the SNP's repeated liaisons with conservative policies have been altogether less toxic for them politically.
By painting independence as the chief policy dividing line they have avoided such comparisons, and successfully marginalised those who do not subscribe to the social democratic salvation of a Yes vote.
Left-wing success in the new Scottish political landscape depends on toeing the SNP's party line.
Recent polling shows the Greens may be the greatest beneficiaries of the crumbs from the nationalist table. By backing the SNP's stance on independence and placing it at the forefront of their policy platform, Patrick Harvie and Maggie Chapman's party have been become the political sidecar to the nationalist juggernaut.
Others are finding it less easy to carve out a position in the new "Yes or No?" Scotland. Labour are sinking without a trace, having given their left to the SNP and ceding their right to the Tories, and Rise are struggling to find a place while at least gamely attacking the weak points in the nationalists' policy platform.
The left-wing guise was claimed by the SNP without a fight, and has been used freely by the party to wage war on Westminster.
Attacks on their "talk left, act right" strategy are increasing by the day, and recent months have finally seen their governing record scrutinised without the usual constitutional whataboutery.
But the battle to snatch back the left from its SNP captors has been made more difficult by the way it was all but voluntarily handed over.
We weren't taken in by Pod People. We invited them in.