Humza Yousaf's job on the line and what happens next to the SNP matters across UK, writes Laura Kuenssberg

"OMG." That's what one SNP politician said to me when they realised First Minister Humza Yousaf had binned a planned public event on Friday morning, fuelling the guessing game about whether or not he'll quit.

In fact, when he popped up in his home city of Dundee in the "busy politician" outfit of hard hat and high-vis vest, he said he wouldn't quit - while also seeming to admit, rather astonishingly, that he had made a horlicks of his breakup with coalition partners the Greens.

"I've heard they're upset, I've heard their anger," he said. "And I can honestly say that was not the intention."

As our Scotland editor James Cook writes, Yousaf, who was cruelly tagged Humza "Useless" by the tabloids even before he became first minister, is in serious danger of being kicked out of office in a few days' time.

His old SNP leadership rival, Ash Regan, member of Alex Salmond's Alba Party, is likely to hold the casting vote when MSPs decide his future. It's not impossible that she backs him - for a political price. Yousaf might keep his job if he gets her vote, but a deal with Alba might mean he loses control of certain policies.

There are no guarantees - and the chances of him being able to get the Greens back on side seem, right now, slim to none.

"It's hard to see him making it to next Thursday," one SNP insider said. "And if he did, it would all fall apart in a few weeks when on every vote, he is stuck between paying a high price to the Greens or selling his soul to Alex Salmond."

The SNP's own MPs are speculating publicly about what might happen next - one saying it's 50/50 that he'll be in a job by the end of the week. Another wrote online that the party "cannot be beholden to the unelectable Alba party", even though making some kind of agreement with that group might be Yousaf's only way to hang on.

Another party source said Yousaf had chosen the wrong approach from the start. "The decision to style his leadership as a continuity candidate misjudged the mood of the Scottish people," the source said. "There were enough rumblings of discontent with gender recognition reform that signified a change of approach was needed."

In other words, Nicola Sturgeon left behind an unhappy party and the electorate had been scratching its head. Perhaps Yousaf failed to spot things needed shaking up.

Whatever happens to the current first minister in the next few days, the bigger problem for the SNP is that this "OMG" moment is just the latest in a long line of nasty surprises for a party that has been in decline, after dominating almost everything in Scottish politics for many years.

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Its leaders, Alex Salmond and then Nicola Sturgeon, were able to make Westminster sit up and pay attention. In election after election, the SNP swept the board with astonishing force. Labour could hardly get a look in, and rarely in Scotland can the Conservatives capture much ground. Sturgeon used to pop up at rallies with thousands of whooping and cheering supporters, and fly around in a helicopter campaigning.

Maybe what goes up, really must come down.

First there was the extraordinary bust up between Sturgeon and Salmond - first minister and mentor turned political enemies - that started with investigations into sexual harassment in 2018.

Inquiries, reports and a huge court case later, the two best known figures in the SNP and the independence movement are politically - and bitterly - estranged. Salmond has a rival party that suddenly finds itself in a powerful position.

Then there was the police investigation and subsequent charge of Sturgeon's husband Peter Murrell; Scotland's governing party embroiled in long running saga into that toxic mix of money and politics.

Intense controversy followed, over changing the law around allowing trans people to change their gender - then Sturgeon's resignation, prompting a bruising leadership contest that put Humza Yousaf in charge.

Unhappiness in Scotland has been building over the standard of public services and the quality of the government at Holyrood - now this nasty and public split with the Greens.

All the while, the SNP has dangled never ending promises that another vote on independence is just around the corner. But the political reality is that the chances of a new referendum have been fading.

The party insider says: "Even without this week's drama, the SNP's big problem is for the last year it's been pulling in different directions not knowing what kind of party it wants to be. It feels like no one is up to the job of leadership."

It feels like a sprawling mess - and it's one that matters. Who's in charge in Scotland affects the tax people pay and how schools and hospitals are run.

It also matters to the rest of the UK, even if you don't feel remotely interested in what goes on in Dundee or Dumfries, in Glasgow or Gretna. The SNP's troubles will have a direct effect on how the other parties fare at the General Election.

Polls right now suggest that Labour is cruising to Downing Street with or without large numbers of Scottish seats. Yet what happens in Scotland, of course, determines the scale of a likely Labour victory. (Don't forget my usual caveat: the election might still be miles away and parties' positions can change very quickly during a campaign).

A government that has a majority of one and a government that has a majority of 100 are not remotely the same. The scale of a victory could be the difference between a new UK government that can make sweeping changes quickly and one that's constantly watching its back, worried it will lose votes in Westminster.

The SNP slide also has an important psychological impact on the two main parties. Labour and the Conservatives both want to claim they can represent the whole UK - now they have a massive opportunity to grab more support in Scotland, and make that promise stick.

And most fundamentally, for as long as the SNP is struggling, the prospect of a vote on independence that could unpick our constitution is far away.

A party source looking hard for a silver lining said: "If the SNP had to have a meltdown, now might be the best opportunity when there's time to sort it out. The only benefit is it's happening when there's no prospect of an Indyref any time soon, so long-term damage to the independence movement can be limited." Let's see.

Just as the SNP's incredible force couldn't last forever, this chaotic period of embarrassment and scandal doesn't have to either.

The party has fallen back significantly in the polls, but it's still vying with Labour for first place. Those kinds of numbers seem only a fantasy for Prime Minister Rishi Sunak these days.

It's notable that despite all the dramas and disasters, the SNP seems to be able to preserve a respectable base. The events of the next few days might determine if there is further to fall.

And yet another major political leader who has held office - following Liz Truss, Boris Johnson, and Nicola Sturgeon - might be out the door.

OMG indeed.

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