On Saturday, what’s left of the SNP will gather in Dundee for its long-awaited Convention on Independence. After a punishing few months the bruised and the battered, the halt and the lame, will hobble towards Caird Hall to discuss how to get their foundational objective back on track.

A version of this conference was planned under Nicola Sturgeon in order to rubber stamp her plan to treat next year’s general election as a “de facto” referendum. That idea – which most people think is a bad one – disappeared with her resignation. The task facing the Nats this weekend is considerably more complex and challenging than it was at the height of the former first minister’s pomp.

You wouldn’t necessarily know this to listen to the top man. Humza Yousaf, Sturgeon’s successor, insisted this week that he would be the leader to deliver independence: a bold and perhaps delusional statement given his party’s seemingly inexorable decline in the polls, and his inability so far to build much personal credibility among the Scottish people.

All the stops are being pulled out in Dundee. Yousaf will speak, as will the internally popular John Swinney, for so long the Bert to Sturgeon’s Ernie. Kate Forbes, narrowly beaten by Yousaf for the leadership and then constructively dismissed by him, is not trusted to give an address – what if she mentioned public sector reform? What if she talked about economic growth? – but is clearly too notable to be left out entirely. She will instead chair a discussion between independence-supporting hacks, which is probably safe enough. The day will end with a rousing call to arms from the deputy leader Mhairi Black, the SNP’s John Prescott. There is no role for the two most significant figures in recent SNP history: Sturgeon is still too closely linked to the police investigation into party finances, while Alex Salmond is of course no longer a member.

The nationalists face a dilemma. Although polls show the party’s popularity is beginning to tumble through space, and tens of thousands of members have quit, support for independence remains at a steady 45 per cent. Voters who backed the SNP in recent years are switching to Labour ahead of next year’s general election, seizing the opportunity to expel the Conservatives from office. Amid a cost-of-living crisis and an NHS crisis, independence is well down the electorate’s priority list.

There must be a risk that a vote for Labour becomes habit-forming – it will be the first time some Scots have done so for many elections, and they might feel quite good about it. If the “time for a change” sentiment becomes infectious, 19 years of underwhelming SNP rule could be ended at the Holyrood election in 2026.

Yousaf has just over a year to arrest the drift to Keir Starmer’s Labour, but it’s hard to spot any emerging policies or insights that might help achieve that. Most of the First Minister’s energy is focused on cleaning up the mess left behind by Sturgeon. He is therefore trying to shore up the base by reaffirming his commitment to independence: the convention will be followed by a “summer programme of independence campaigning activity, including leafleting, canvassing and regional assemblies”. There will also be more in the rambling series of independence papers being tossed out by civil servants. All roads lead to the SNP’s annual conference in October, which “will officially decide our independence strategy”.

It remains to be seen what impact all this effort will have. My impression – and the polls seem to support it – is that only the SNP hardcore is interested in talking about independence at present. It’s a monomania that looks increasingly out of line with the public interest and indeed the public’s interest, the sign of an exhausted party retreating behind the compound walls. But what is the SNP without its singular obsession?

Scottish Labour, meanwhile, is on the rise. A poll last weekend put the party on course to win more Westminster seats than the Nats, which will have sent a jolt of adrenaline through leader Anas Sarwar and his team. The view inside Labour is that Yousaf is a man slipping off a cliff, scrabbling hopelessly for the rocks around him. Sarwar intends to step on his fingers.

This, then, is a moment of hope – at long last – for those who are either opposed to or unpersuaded by independence. Even the Scottish Tories seem quite pleased. As ever, though, wisdom dictates that optimism in the short term should be coupled with a dose of longer-term pessimism.

The SNP deserves a period in opposition due to its longevity in office – and it will probably get one. The party will then have two choices. It can either spend years arguing about the minutiae of independence and denouncing the faithless electorate, or it can do what the other parties tend to do when they lose power after a period of hegemony: rethink from the ground up.

You can’t come back with the same old people making the same old offer. It’s not what Tony Blair did in 1997, and it’s not what Keir Starmer is offering now. It’s not what David Cameron did in 2010. Accept that an era has passed and that fundamental reconstruction is required at the policy and strategy levels. This was the analysis applied by Salmond before he took the SNP to power in 2007, and the same needs to happen again. It will require a rediscovery of patience, strong internal challenge and probably better brains than are currently at the party’s disposal. Where are its Blairs and Mandelsons and Campbells? Where are its Camerons and Osbornes and Goves? I’m sure the suggestion rankles, but these are the kind of figures you need.

For Labour’s part, pessimism matters because the Nats might get it right. For some Scots, a Starmer government will be their last shot at making the Union work. There are expectations attached to their vote, which do not align with his Tory-lite policies on immigration and Brexit. They understand Labour must compromise to win, but they will expect to see progressive movement in these areas following victory. They will want to see that Britain is not a country locked into inevitable decline, where the weakest suffer the most. And they will expect a better, more constructive relationship between Westminster and Holyrood. If Labour fails, the Union may yet founder.

Starmer’s repeated trips north of the border suggests he gets this in principle, at least. But he will ultimately be judged by Scots on what he does in the years ahead, rather than what he is saying now.