A hundred days ago, when Humza Yousaf was sworn in as First Minister, it was clear something big was happening. Scottish politics was entering a period of flux that would change the balance of power. The SNP’s simmering internal divisions had boiled over during a fractious leadership contest and its dominance of Scottish politics was faltering as Labour’s star rose.

Questions swirled. How far would the SNP’s diminishing popularity slide? Did Mr Yousaf have the attributes to be First Minister? And would he follow Nicola Sturgeon’s programme and tactics, or be his own man?

Three months on, the SNP’s poll ratings have declined further. The downward trajectory was set in January, under Ms Sturgeon, amid controversy over gender recognition legislation and a mounting list of policy failures. But the shock arrest of Ms Sturgeon’s husband Peter Murrell for questioning as part of an investigation into SNP finances a week after Mr Yousaf took office, the appearance of a police tent on the couple’s lawn and news that a certain campervan had been seized – followed by the arrest of Ms Sturgeon herself – has not helped. (Both husband and wife were released without charge.) At the same time, Mr Yousaf has had to carry the can for a series of Scottish Government failures.

The circumstances could hardly have been tougher – but he’s held it together. Mr Yousaf has shown himself to be calm under pressure, prone to outbursts of pragmatism and more humble about the SNP’s electoral prowess than his predecessor was.

We’ve seen him sensibly change the Scottish Government’s position on the Deposit Return Scheme (albeit without accepting Scottish ministers’ part in the mess), rejoin international education surveys after a decade, and stop the Highly Protected Marine Areas plan that angered so many coastal communities.

He has been deliberately careful about what his government can achieve between now and the next election, against a backdrop of voter scepticism.

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We’ve heard him inject some credibility into the debate on independence issues like the Euro (Scotland would have to agree to join in principle), border checks on goods (yes, they would exist) and Faslane (Scotland would face negotiations with the UK, US and Nato to have nuclear weapons removed).

There are glimpses here of a thoughtful, clear-sighted politician who understands the mess he’s in; that his party is losing voter trust and that continuing Nicola Sturgeon’s habit of overpromising and underdelivering, won’t win it back.

So how do we reconcile this down-to-earth figure with the ludicrous plan he has served up on achieving independence? It’s very hard to match them up, which in itself tells us something: that Humza Yousaf is just as beholden to the independence fanatics in his party as Nicola Sturgeon was.

Last month, he declared that if the SNP won a majority of seats in the forthcoming general election, then it would be a mandate either to start negotiations with Westminster on separation or to have a referendum, a rather messy, confusing position. Insiders insist this differs from Ms Sturgeon’s approach (that winning more than 50 per cent of votes would be a mandate to start independence negotiations) but it sounds an awful lot like another de facto referendum.

Either way, it’s unconvincing. The SNP more than any other UK party benefits disproportionately from FPTP. The SNP could conceivably win a majority of general election seats on less than two fifths of the vote, with a majority of voters backing parties that opposed independence – an absurd position from which to claim an independence mandate.

And anyway, people vote on numerous issues in a general election, not just the constitutional question.

But it’s what Mr Yousaf said next that reveals his real intentions. He promises that if the SNP wins a majority of seats, a “withdrawal” document will be published setting out the independence terms Scotland seeks. A nationwide consultation will take place on a draft constitution for the “newly independent state”. Next an envoy will be sent to Brussels.

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This plan amounts to a massive, protracted campaign of grievance-mongering.

Why would a politician who believes independence can only be won by persuading voters on policy, go down this antagonistic path? Why else but because of the need to manage divisions in the independence movement. Potentially fatal fissures are emerging within it and the SNP’s leadership of it is more vulnerable than ever. Rather like Rishi Sunak, desperate to keep hardline rightwingers on side, Mr Yousaf must appease his own impatient supporters with fantasies.

This is a very, very big risk for a party that the country has started falling out of love with. The SNP’s independence tubthumping, while public services decline and the cost-of-living bites, risks making it and its leader look increasingly irresponsible, obsessive and out-of-touch.

Mr Yousaf faces other risks. In spite of the controversy surrounding Nicola Sturgeon, he has refused to break faith with her. Indeed, he’s embraced the association, declining to suspend her following her arrest (in spite of the precedent she herself set) and describing her as “the most impressive politician in Europe”.

He has lashed his reputation tightly to hers.

Some see this as a sign of weakness, but there is a certain bloody-minded honesty in it. Everyone knows Humza Yousaf was the candidate favoured by Ms Sturgeon. A disavowal of her would have seen Mr Yousaf accused of weaselly disloyalty and could ultimately have backfired on him. Nicola Sturgeon does strongly insist on her innocence.

Unfortunately for Mr Yousaf, the risk of this close association does not just come from the police investigation into SNP finances, but from the growing sense that the government Nicola Sturgeon led for so long is underperforming.

The overbudget, overdue Western Isles ferries, NHS waiting lists, the mishandling of the deposit return scheme, faltering standards in schools, glacial progress in dualling the A9, the lack of popular support for gender recognition reform, plans for a National Care Service that lack credibility and a police force facing dire budgetary constraints: the problems from Ms Sturgeon’s era are manifold and Mr Yousaf has to carry the can.

The first hundred days have been tough for him, but the next hundred could be even harder.