When Scottish Labour politicians and activists gathered at their annual conference a year ago, it was with a newfound optimism, despite doing so under overcast Edinburgh skies. The catastrophe of Liz Truss’s premiership had catapulted Labour to poll leads they hadn’t enjoyed since Tony Blair’s first term in office, elevating Scottish Labour above the Scottish Conservatives to become Scotland’s strongest unionist party.

Nevertheless, despite the shock announcement of Nicola Sturgeon’s resignation, they continued to trail the SNP by double-digit margins. A general election would have returned nearly 50 SNP MPs and fewer than ten for Scottish Labour, who continued to face the vexatious question of how to eat into the SNP’s remarkably durable base of independence supporters.

But a year is an eternity in politics. As Anas Sarwar’s party meet in Glasgow this weekend, the silver linings of those Edinburgh clouds have given way to sunny skies – politically, at least.

They convene on the heels of two colossal by-election wins in England, overturning Conservative majorities of 11,220 in Kingswood and 18,540 in Wellingborough, achieving the second-largest Conservative-to-Labour swing in a by-election since 1945.

In the ten English by-elections since Rishi Sunak became Prime Minister, the Conservative-to-Labour swing has been over 15 points, enough to deliver around an 18 or 19-point Labour victory if replicated in a general election – greater than Margaret Thatcher’s record-setting 14.8-point win in 1983.

Even if we slash that lead by a third to a more realistic 12 or 13 points, we’re talking about a 1997-level Labour victory and at least one of the three or four largest margins of victory in postwar British electoral history.

And just a few months ago, Scottish Labour scored a significant victory over the SNP by winning the Rutherglen and Hamilton West by-election with the fourth-largest swing in a postwar Scottish parliamentary by-election.

In the past year, Scottish Labour have found themselves beneficiaries of a divisive SNP leadership election, the dramatics of Operation Branchform, and the Yousaf government’s preference for shooting itself in its front foot instead of putting that foot forward.

The SNP’s missteps have boosted Scottish Labour over that first hurdle to defeating them without Anas Sarwar’s party having to do much work for it.

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Polls suggest that Scottish Labour could win a narrow majority of Scottish seats in the upcoming general election, helping Labour to a substantial majority in the House of Commons. But more importantly for Mr Sarwar and his team, they also put them in contention to become the largest party in the Scottish Parliament for the first time since 2011.

So the challenge facing Scottish Labour is no longer how to get independence supporters to give them a second glance – the SNP have seen to that – but now that they have an audience, the harder question of how to construct and hold together a coalition of voters that straddles the constitutional divide.

In May 2021, Scottish Labour’s vote was overwhelmingly composed of voters who opposed independence and had voted for the party during the Corbyn years. According to a Survation poll on the eve of the Scottish Parliament elections, 72% of Scottish Labour voters opposed independence, with just 14% in favour. Two-thirds had voted for Scottish Labour in 2019, with the rest saying they had voted for various other parties.

A year ago, that voter coalition had expanded and shifted. Less than half of those who told Survation they would vote for Scottish Labour at the next election had voted for the party in 2019, while the proportion who had voted Scottish Conservative in 2019 had doubled. The chunk who supported independence was essentially the same as in 2021.

But today, Scottish Labour’s support is much more diverse. In the latest Survation poll, barely more than two-fifths of Scots who say they’d vote Labour voted for the party in 2019. One-eighth voted Conservative, and a quarter of Scottish Labour’s vote now comprises 2019 SNP voters, more than double the share in 2021.

And a quarter of those who would now vote for Scottish Labour support independence, with three-fifths opposed.

Throughout this period, Scottish Labour’s theory has been that the importance of independence as an issue for voters would decline and that the constitutional question would ultimately go away, at least in the short term, allowing them to contest elections on more traditional grounds.

But this has not been the case. According to Redfield and Wilton’s polling a year ago, 21% of Scots said the constitution was among Scotland’s three most important issues, including 34% of 2019 SNP voters. Their latest poll at the beginning of February found that exactly the same share of Scots thought the constitution was a priority, including 35% of 2019 SNP voters.

What has changed is that rather than maximising the number of pro-independence MPs at Westminster, some pro-independence voters are prioritising a mix of kicking the Conservatives out of office on the one hand and protesting the SNP’s failures on the other.

But unlike in England, Scottish Labour do not have any appreciable polling lead in Scotland. The difference between a Scottish Labour minority and another SNP-Green majority at Holyrood is paper thin. If Anas Sarwar wants to be First Minister after the 2026 Holyrood elections, he has to find an offer that retains pro-independence Scots’ support.

And if he wants to govern without the support of Conservative MSPs, he will need to win the support of significantly more pro-independence Scots than he already has.

Unfortunately, any hope of meaningful constitutional reform that might have appealed to such voters has been snuffed out. As the SNP strive to raise the salience of the constitution ahead of the 2026 elections, Mr Sarwar will have little to offer pro-independence voters as a compromise.

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Instead, this weekend Mr Sarwar will invite Scots to judge him on what Labour does for the economy, hitching himself to the reputation of a post-honeymoon Westminster government that the SNP will do everything they can to discredit.

These are huge gambles for Scottish Labour, and the assumption that the biggest driver of Scottish voting behaviour for the past decade won’t play a significant role in the coming years is dangerous. I’m sceptical that those gambles will come off. But whoever won power without taking risks? Fortune, after all, favours the bold – or so Scottish Labour will hope.