The Scottish electorate went to the polls in 2014 in what then First Minister Alex Salmond had termed a "once-in-a-generation" event which saw 55% of the country vote to remain part of the United Kingdom. The 2016 Brexit referendum, however, led to fresh calls for a second independence vote due to 62% of Scots voting to remain in the European Union which was at odds with the overall UK picture with 52% of the electorate opting for the leave option.
Support for Scottish independence has also grown since the referendum with polls over the past year showing support for the break-up of the UK at consistently over 50%. This has bolstered the SNP who pledged in their 2021 Scottish Parliament election manifesto to hold a second referendum within the next term of the Scottish Parliament.
Today's expected result will see First Minister Nicola Sturgeon approach the Scottish Greens to form an independence supporting partnership.
Speaking on BBC Radio 4’s today programme on Saturday morning, the deputy SNP leader, John Swinney, said that the agreement, in place of outright majority for the SNP, would be a sufficient mandate for a second referendum.
Swinney said: “I don’t accept that proposition because I think what that question comes down to is what’s the composition of the Scottish Parliament, and who tried to get elected to it. And I’m very confident of two things.
“One, that the SNP will be the leading party after the elections. It is very clear that’s going to be the case. And secondly, I’m certain there will be a majority in the Scottish Parliament of people who are committed to the holding of an independence referendum on the future of Scotland.”
Coree Brown Swan, deputy director at the Centre on Constitutional Change at the University of Edinburgh, said that she expected the UK Government to use the majority issue in arguments against a second referendum.
She said: "I do suspect that the UK Government, if the SNP does not achieve a majority government, would use that as a reason for pushing the referendum back.
"There has never been a defined threshold for a majority in the Scottish Parliament or a defined process to which you could hold another referendum.
"With the Greens, the SNP will be able to form a pro-independence majority within Parliament.
"If you have enough votes to pass the legislation then surely that's a legitimate vote?"
SNP's next move
First Minister Nicola Sturgeon, following her re-election as MSP for Glasgow South, said that she would initiate moves for a second independence referendum "when the time is right."
Ms Sturgeon said: “If that is indeed the outcome of this election, I pledge today to get back to work immediately to continue to steer the country through the crisis of Covid, to continue to lead this country into recovery from Covid.
“And then, when the time is right, to offer this country the choice of a better future.”
Sturgeon also told Channel 4 News that the SNP would introduce the legislation for a referendum before 2023 “and if Boris Johnson wants to stop that he would have to go to court”.
“If this was in almost any other democracy in the world it would be an absurd discussion. If people in Scotland vote for a pro-independence majority in the Scottish parliament, no politician has got the right to stand in the way of that.”
Coree Brown Swan said that the two governments were on a "collision course" that would likely end up in the courts.
She said: "The two governments are definitely on a collision course because at some point the UK Government is going to have to mount a legal challenge and the Scottish Government is going to have to respond.
"I think there is a strategic incentive for the UK Government to allow a second independence referendum when the economics are very uncertain and hope that they can win but that is a gamble.
"The constitution is going to remain firmly on the agenda of UK politics and right now it is a game of chess to see who moves first and how the other party responds."
The SNP leader has two potential routes to a second independence referendum.
The first would replicate the process used in the 2014 Scottish independence referendum in which the UK Government granted a Section 30 order which altered the Scotland Act and gave the Scottish Parliament permission to hold a referendum by December 31, 2014.
Boris Johnson today, however, has reiterated his opposition to a second referendum meaning a Section 30 order in the lifetime of the next Parliament is unlikely.
He told The Telegraph: “I think a referendum in the current context is irresponsible and reckless.”
“My impression was that they [the SNP] moved away from the idea of a referendum, and I think very wisely.
“I don’t think this is anything like the time to have more constitutional wrangling, to be talking about ripping our country apart, when actually people want to heal our economy and bounce forward together. That’s what people want.”
The second option would see the Scottish Government pass a bill in the Scottish Parliament to enable a second referendum.
This option, however, is far from clear cut and would likely be met by a legal challenge from the UK Government who would argue the bill contravenes reserved powers within the Scotland Act covering the constitution.
The Scottish Government could however counter that the act of holding a referendum would not contravene the act however it is the matter of whether the referendum would be binding or not which is a grey area.
With a Section 30 order unlikely and the UK and Scottish Government's at odds over the permissions provided by the Scotland act, it is looking increasingly likely that the matter will be presented to the UK Supreme Court for a decision.
Coree Brown Swan said that she did expect any movement from the Scottish Government in the short term.
She said: "There won't be an immediate move to another referendum as Nicola Sturgeon has not included it within her proposals for her first 100 days.
"I expect we will see a lot of posturing between the two governments before a vote is held in the Scottish Parliament on a second referendum and it will then be up to the UK Government to challenge it.
"We do not know how the UK Supreme Court would respond given a previous referendum has been held and their preference for political rather than legal solutions."