JK Rowling has blasted "Karma's a b***h" as SNP leader Humza Yousaf faces backing down on gender to save his job.
Yousaf's government is in meltdown after he ripped up the SNP's power-sharing deal with the Greens.
He now faces a at the Scottish Parliament next week.
His fate is potentially in the hands of Alba Party MSP Ash Regan, who defected from the SNP last October in protest at its gender stance.
Yousaf called Regan "no great loss" after she quit the SNP - but now needs her backing in the knife-edge vote.
Regan has now written to Yousaf laying out her demands in return for propping him up.
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The demands are thought to include "defending the rights of women and children" and backing down on trans legislation.
Posting on Twitter, JK Rowling said: "Humza Yousaf's political fate may now lie in the hands of Ash Regan, the woman who left the SNP in disgust at its plans for gender self-ID.
The Harry Potter author shared a picture reading: "They say Karma's a b***h but I hear she's a Terf."
An abbreviation of "trans-excluding radical feminist", Terf is an insult often directed at critics of gender legislation like Rowling.
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She has previously slammed rules which campaigners say make it illegal to refuse to call a biological man a woman in Scotland.
This morning Regan told BBC Radio 4: "I’m not setting out specific demands, as such.
"I am really putting the ball into Humza’s court for him to come back to me and explain how he will make progress in a couple of areas.
"Particularly around the return to a competent government. This is something the SNP was obviously known for a few years ago.
"Unfortunately, it’s lost its focus, over the last few years it has gone down pursuing some policies that are not popular with the public.
"Many of those were policies that really stemmed from the coalition agreement with the Green Party.
"I think many people in Scotland will be very pleased to see the end of Green Party extremism coming from the Scottish Government."
Nats MP Stephen Flynn called for “cool heads” and “calm words”, after Mr Yousaf .
But Yousaf has today cancelled a major speech on independence - just an hour after claimed he would “come out fighting”.
Mr Yousaf was due to speak on his economic plans for an independent Scotland at Strathclyde University.
He was then due to take questions from an audience of academics and guests, followed by media interviews.
understands Mr Yousaf's aides have been trying to organise another, more "low key" event for him to attend today.
Flynn told the BBC: "Now is a time for cool heads, it’s a time for calm words.
"It’s a time to remember that the public are watching, the public are listening.
"The public have very high expectations of their politicians and rightly so.
"It’s now the case MSPs and Holyrood need to rise to those expectations."
SNP Westminster supremo Flynn added: "Humza Yousaf is a man of profound integrity.
"I had a conversation with Humza last night after both our kids were put to bed.
"You know, he was reflective but he was also very clear to me that he is going to come out fighting.
"He believes in what he says, he believes in delivering for the people of Scotland.
"What I expect to happen next week is that the First Minister, the leader of my party, wins that vote next week.
"He will continue to be the party leader and he will continue to be the First Minister of Scotland.
“Now is not a time to speculate over the future of anyone beyond, of course, the discussion that is being had next week.
“The First Minister has my full support, I believe he is going to come out fighting today.
"I’ll be standing shoulder to shoulder with him during that battle."
Scottish Greens co-leader Lorna Slater said: "We had been a stable, progressive government.
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"As things unravel so rapidly, I think it will become clear the Greens were the glue holding stable governance together in Scotland.
"Whether he can hold together a government now, I don’t know."