Scottish election 2021: Can independence supporters force another referendum?

In the first of a two-part series looking at the Scottish election, we explore the differences inside the pro-independence movement. 

The election in Scotland on 6 May matters - and not just to people in Scotland. It could have a significant impact on the future of the union.

If there is a pro-independence majority in the Scottish Parliament again, calls for another referendum will continue to be a significant part of UK politics.

The UK government says the last referendum was "once in a generation" - and a generation hasn't passed. Recent polls have suggested opinion in Scotland remains on a knife-edge and the process for another referendum remains the subject of much argument.

But if the SNP win a majority on their own - they will argue they have a cast-iron guarantee for another referendum. They could also have a pro-referendum majority with the support of other parties in Holyrood.

Despite this, there is still more tension in the independence movement than we've seen in many years.

SCOTLAND ALERTS: Get extra updates on BBC election coverage

The SNP have been the dominant force in Scottish politics since the 2014 referendum. They've won every election to Holyrood and Westminster comfortably. Even before that, the party had been in power for seven years in Edinburgh. Ms Sturgeon's party is now asking voters to extend a 14-year spell in charge for another five years.

A big part of the pitch is that the Scottish government is best placed to manage Scotland's recovery from the pandemic. As part of that Ms Sturgeon argues Scotland needs more powers to make decisions about its future.

The party's manifesto pledges another independence referendum in the next Holyrood term - ideally in the first half. That would mean the next two-and-a-half years.

There is one caveat; that the referendum will only take place "if the Covid crisis has passed". That's designed in part to answer the charge that the SNP would be distracted in the midst of a pandemic (we'll look in more detail at the unionist arguments later this week). It also gives the SNP a bit of leeway on when the referendum should be.

I asked the SNP's finance secretary Kate Forbes - tipped by some as a possible successor to Nicola Sturgeon - whether this election was primarily about independence for her party.

"It's about a number of things - but ultimately yes, it's about Scotland's future and the constitution is key to that," she said.

"This election is about who we trust ultimately to lead Scotland's recovery - and what powers and levers we need as a country to deliver a robust recovery."

The SNP believe that if they win a majority, it will put huge pressure on Boris Johnson to agree to another referendum - despite the fact he's said up until now that he won't give his blessing to one any time soon.

"If the Tories continue to say no to another referendum, then the union is completely changed," said Ms Forbes. "What was once a union of equal partnership based on consent will have become a union that only survives through force of law."

She added: "The only time there's ever been an independence referendum is when the SNP delivered it because the SNP had a simple majority. It's a tried and trusted way of delivering not just a process that's watertight - but an outcome that's watertight."

The UK government - and unionist parties more generally - would disagree. They see this as a distraction when Scotland is recovering from the pandemic.

The simple SNP message is this; if you want another referendum, the SNP can deliver it.

But on the independence side, some are getting itchy feet. That's where Alex Salmond comes back in.

SCOTLAND'S ELECTION: THE BASICS

What's happening? On 6 May, people across Scotland will vote to elect 129 Members of the Scottish Parliament (MSPs). The party that wins the most seats will form the government. Find out more here.

What powers do they have? MSPs pass laws on aspects of life in Scotland such as health, education and transport - and have some powers over tax and welfare benefits.

Who can vote? Anyone who lives in Scotland, is registered to vote and aged 16 or over on 6 May is eligible. You can register to vote online.

In the run-up to this election, Nicola Sturgeon and Alex Salmond were engaged in a bitter and very public battle over how her government handled harassment allegations against him. He has now launched a new party, Alba, which has thrown a grenade into the election campaign and the wider independence movement.

Mr Salmond has accused the SNP of lacking urgency when it comes to delivering independence.

"In one month's time there should be a motion in the Scots Parliament instructing the Scottish government to initiate independence negotiations with Westminster," Mr Salmond told me for Radio 4's PM programme.

He added: "The idea you wouldn't want to be negotiating independence while we're negotiating the reconstruction...I think betrays a lack of understanding of how important independence is."

Mr Salmond is increasingly at odds with the SNP about how independence could be achieved too.

Remember the SNP says the only way is a referendum, which is legally and internationally recognised.

Mr Salmond told me he does not now think a referendum is essential - citing the example of the Czech Republic and Slovakia.

"Do you have to have a referendum? No, there are other routes and agreements. You have to have some sort of democratic, accepted test, so that would be part of the negotiations," he said.

The idea of independence without a referendum will anger many unionists - and likely some in the SNP.

It's hard to imagine Nicola Sturgeon would enjoy the prospect of her former mentor turned bitter enemy sitting in the Scottish Parliament - urging her to be more militant on independence.

Alba are a new party and it's hard to say with any certainty how they are doing. Polls suggest they may struggle to win seats - an average puts them around 3%, although some polls have suggested a higher figure of 6%.

But senior figures still seem confident of making a breakthrough on 6 May. One told me recently that despite the polling, on a good day they could win 14-18 MSPs. Senior SNP figures think that's unlikely - to put it politely.

While Alba are a new party and polls suggest they may struggle to win many seats, there is a pro-independence party which has a track record of returning MSPs at Holyrood.

Although the SNP fell just short of a majority at the last Scottish election, when you factor in the Greens, there was a pro-referendum majority in the last Holyrood parliament.

The parties agree another referendum should be held in the next Holyrood term. There has been some criticism, primarily from anti-independence parties, that the Scottish Greens and SNP are too similar.

That's an argument rejected by Lorna Slater, the Scottish Greens' co-leader.

"The SNP is very much business as usual, they are committed to keeping things the way they are… we think the whole point of being independent is to do things differently, to change where power lies," she said.

Much will depend on how the regional voting system in Holyrood pans out.

More Green MSPs, Ms Slater adds, will push the SNP to be "greener and fairer".

But could that come through a coalition? If the SNP fall short of a majority, or if they want a bigger one, some have suggested a formal arrangement could be the answer.

Ms Slater doesn't seem convinced.

"There has been no discussion between the parties about a coalition, that is purely media speculation," she said.

"There are enormous policy differences with a political party that sides with developers - and wants to maximise oil and gas extraction - and that doesn't hold the same views we have on a lot of things.

"That would be a very difficult thing to bring together. Unless we were in a position to have those talks, we'll have to wait and see what the voters say."

In just over a fortnight, they will have the chance to do just that.