In a UK general election year, it may prove difficult for the SNP to find alternative partners to win votes on anything even slightly controversial.
If there was a confidence vote in a government minister for instance, the combined forces of opposition at Holyrood – now including the Greens – could beat the SNP.
That’s one reason some in the SNP may be sorry to see the Greens go.
Their power-sharing deal was about creating stability for the SNP and achieving greater influence and credibility for the Greens.
There was a potential longer term project too.
Some imagined an official or unofficial pact between the parties at the next Holyrood election, with the SNP targeting constituencies and the Greens focusing on the top up lists.
That strategy would have aimed to keep both parties in power and maintain an independence supporting majority in the Scottish Parliament.
New strategies will now be required for both parties – and that may involve some change in the leadership of the Scottish Greens sooner rather than later.
It does not necessarily secure Humza Yousaf’s position at a time where the SNP have been sliding in the opinion polls and Labour are experiencing a revival.
My expectation has been that Mr Yousaf would lead his party into the next general election and his position after that be determined by the extent of any losses.
More immediate doubt has been cast on his political survival with the Conservatives proposing a confidence vote in the first minister at Holyrood.
The SNP government is in no position to guarantee that Mr Yousaf will win the vote the Conservatives.
If all opposition MSPs, which now include the Greens, vote no confidence in the first minister he would lose.
Strictly speaking, that vote is not binding but politically he would more or less be obliged to resign and the prospect of an early Holyrood election would start to loom large.
So how could he survive this challenge?
If the Greens cool down over the next week and rather than voting against Mr Yousaf choose to abstain – or if any one opposition MSP could be persuaded to switch sides.
The SNP have 63 MSPs. Their opponents have 65. One switcher to the government could result in a tie in which the presiding officer (equivalent of the Commons speaker) would be expected to back no change.
If the government cannot engineer either of these scenarios Humza Yousaf’s political survival would be in serious doubt.
