This article appears as part of the Unspun: Scottish Politics newsletter.

Are we about to enter uncharted territory in Holyrood? Could this be the year the Scottish Government fails to get its budget through?

In recent pre-Bute House agreement years there was always a bit of a dance. The Greens would say they’re not going to back it, the SNP would say are you sure, the Greens wangle a wee bit something extra and then they do.

Not this time though.

We’re in a post-Bute House Agreement world and after Tuesday’s savings and Wednesday's Programme for Government, the Greens - who have backed every SNP budget since 2016 - are pretty furious.

Commitments on the conversion therapy ban, peak rail fares, the nature restoration fund, rent controls, and free bus travel for asylum seekers have all, says Lorna Slater, been “undone, slashed, watered down or shelved.”

In the chamber, she even used the word “betrayal”.

It’s hard to see the path from betrayal to backing the budget.

If the SNP’s Budget Bill is defeated at Stage 1 or at Stage3, then the government can try again or tweak it or bring in a completely new Bill.

Failing to get a Budget Bill passed does not automatically bring down the government, but a government that cannot get its Budget Bill passed clearly does not have the confidence of Parliament.

That could mean a vote of no confidence in the government, which, if successful, could mean the First Minister resigning, which could then put us in a situation where MSPs cannot agree on a replacement within 28 days, which could then trigger an extraordinary general election.

During the SNP’s first stint as a minority government between 2007 to 2011, the then first minister Alex Salmond and his finance secretary, John Swinney, were able to pass their budget thanks to the support of Tory MSPs.

However, things got a bit trickier in 2009 when its draft budget was defeated by the casting vote of the parliament’s presiding officer, who by convention votes with the status quo.

Rather than risk a snap election, an amended budget was presented a week later and passed with the support of Labour, Tory and Liberal Democrat MSPs.

The Holyrood arithmetic means John Swinney needs the support of one other party to get his spending plans through.

There are 129 MSPs in Parliament and the First Minister needs 65.

Currently, he has 62.

We can assume John Mason will probably back the budget - though we still don’t know how long his administrative suspension over social media comments on the war in Gaza will last.

There still needs to be a meeting of the party’s member conduct committee, before the Holyrood group can take action.

It could be that he’s still out of the party when the vote comes in February. Or it could be that he’s not allowed back in at all.

And if there’s something he’s unhappy about, well… For the meantime let’s put him in the mebbe aye pile. That’s 63.

Sign up and get Scotland's top politics newsletter straight to your inbox.

Could Alba’s Ash Regan be tempted? An Alba source says they will need to see “action on independence, a drive towards governing competently again and focus to be put back onto the people’s agenda of health, the economy and jobs.”

The party say they are hopeful Ms Regan “will have the opportunity to raise specific policy matters with the Scottish Government for inclusion in the budget if the First Minister meets with her ahead of its draft publication.”

Particularly, they would like support for her bid to bring in the Nordic Model in Scotland, and create an offence of paying for sexual services.

So lets, for the sake of argument, give the First Minister Alba’s support. That takes him to 64.

Labour and Tory sources insist that when the time comes they will enter negotiations with the SNP in good faith.

But there are red lines and a looming Holyrood election and can either party really prop up John Swinney’s administration?

That seems unlikely.

Which leaves the Lib Dems.

Can they be bought off? If one of them can be convinced to abstain, then John Swinney only needs the 64.

The FM is, we're told, a deal-maker and the Lib Dems say they’re amenable to a deal.

But the SNP don’t seem mad keen.

“This doesn’t feel like a governing party that’s trying too hard to make friends,” a source told the Times.

"Perhaps they have no intention of passing a budget and perhaps we are going to the country sooner rather than later.”