HUMZA Yousaf faces the biggest challenge of his political career as all major parties have declared they have no confidence in the first minister.

These sorts of challenges aren’t uncommon in the Scottish Parliament – Lorna Slater and John Swinney have both survived confidence votes in recent years.

This one’s different. If the First Minister cannot command the confidence of the Parliament, while theoretically he can stay on, his position becomes untenable politically.

His future now lies in the hands of former colleague Ash Regan (below), Holyrood’s sole Alba MSP. Yousaf had described her as “no great loss” when she quit his party for Alex Salmond’s outfit last year.

The National: Ash Regan

Regan may be unlikely to want to tank an SNP government – however shaky its foundations – given her party will be wanting SNP voters’ second preferences come a Scottish Parliament election.

If she backs him, Yousaf survives. She will write to Humza Yousaf on Friday morning, with a list of demands on which she needs solid commitments before guaranteeing her support.

READ MORE: Inside the room as Humza Yousaf sacked the Scottish Greens from government

These include support for her Referendum Bill, which has so far been stalled because the SNP have refused to support it.

The bill, unveiled late last year, would legislate for a referendum on whether Scots think Holyrood should have the power to hold indyref2 – a referendum on a referendum, essentially.

The National: Humza Yousaf

That may be easy for Yousaf (above) to swallow – but he will also need to concede to Regan’s demands around “women’s rights [and] child protection”.

This runs the risk of Yousaf alienating large amounts of his MSPs, many of whom backed trans rights policies to the hilt.

READ MORE: Scottish Greens to back vote of no confidence in Humza Yousaf

Even if he clings on, he still must deal with the difficulties of running a minority government.

To put this in perspective: earlier this week, Yousaf managed to pass plans for juryless rape trials by the skin of his teeth even with Green support and MSPs abstaining outnumbering those in favour.

Yousaf is not known for his conciliatory approach in the chamber – and he will struggle to make alliances on the Tory and Labour benches – even if he can stop bickering with them at FMQs.

In the event Regan decides it’s time for Yousaf to go, he must decide whether he will stay on as First Minister or resign.

In the likely event he takes a no-confidence vote as his cue to step down, the question of who will replace him becomes urgent.

Kate Forbes has been touted by some, but given her views on LGBT issues and abortion proved so divisive in the SNP leadership contest, she may be a long shot.

Another possibility is John Swinney, a well-respected figure across Scottish politics but someone who has indicated their time on the front lines is over.

Whichever way things go over the next few days, it seems unlikely Yousaf that will be getting an easy night’s sleep for a while.