“HOW lovely yellow is, it stands for the sun”, said Vincent van Gogh. This week, Sir Keir Starmer and Anas Sarwar, leaders of the Labour party north and south of the border, may not agree.

They have political walls to break if they are to win the General Election, expected within the next 18 months. The most famous of these is the red wall – those seats in the north of England which are characterised as former Labour strongholds but which support Brexit, and therefore supported Boris Johnson’s Conservative party in 2017 and, even more so, in 2019.

Then there is the blue wall – those traditionally Tory seats across the south of England which opposed Brexit, but were so repulsed by the prospect of Jeremy Corbyn being their Prime Minister that they placed it to one side.

Labour appears to be doing a decent job of removing the bricks from those walls. In the north of England, pollster Redfield and Wilton Strategies records a sustained lead for Labour of between 10 and 15 per cent, having lost by the same margin at the 2019 General Election.

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Sir Keir has a positive approval rating there, probably helped by his refusal to adopt a position of rejoining the European Union, and whilst neither he nor his party are yet wildly popular, they appear to be well-enough regarded to win back a healthy chunk of those seats.

Similarly, in the blue wall, they are fending off the Liberal Democrats and attracting fleeing Tory voters. A full 30 per cent behind in 2019, Labour and the Tories are now neck-and-neck, with the Lib Dems, hopeful of juxtaposing their pro-EU stance with Sir Keir’s reluctance, struggling to make an impression.

Breaking these walls may be enough for Sir Keir to take the keys to Downing Street, either by way of a slim majority or with a little help from his friends in the Liberal Democrats. However it seems unlikely that he will be able to enjoy a larger, healthier majority without smashing a third wall – the SNP’s yellow wall of Scotland.

Progress is being made. Labour’s support across Scotland has moved from the high teens to the high twenties, and seat predictions extrapolated from polls suggest they will almost certainly win more than a dozen seats, and, on a good night, double that. Thus far, though, the increase in support has come from those voters who have hitherto been lending their vote to the Tories.

This is not insignificant. These soft unionists, pragmatists driven primarily by a determination to avoid independence, began to vote Tory because they saw them as the safest bet to stop a second referendum. However, with the Supreme Court having stymied the Scottish Government’s ambition to assert its authority to hold a referendum, and with the Tories looking like moving out of Number 10, the motivation for a non-Tory to vote Tory has gone.

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Labour has them back, almost for free. But winning over their counterparts, the soft nationalists, will cost more. There are signs that a few of them have drifted towards Sir Keir and Mr Sarwar. The presumption that the UK will be run by Labour, and not the Tories, in-and-of-itself de-risks voting Labour and removes one of the drivers to vote SNP.

But polling is showing us that this, on its own, is not enough. A detailed survey this week, also by Redfield and Wilton Strategies, shows a decline in Labour’s favourability and an increase in that of the SNP. Humza Yousaf remains comfortably ahead of Anas Sarwar in their head-to-head ratings. The SNP remains in a healthy lead in voting intentions both for Westminster and Holyrood.

In short, soft nationalists are strolling to Labour in small numbers, while Labour needs them to run in droves. The solution to this problem is staring them in the face, and it comes back to the omnipresent matter of Scotland’s constitutional future.

Labour is in a simultaneously precarious and privileged position when it comes to defining the future structure of the UK. The party’s voter base is mixed. There are dyed-in-the-wool unionists, there is a (for want of a better term) federalist community and, increasingly, there are supporters of independence. Finding a way through that, whilst delicate, could be extremely lucrative.

That way through will inevitably involve creating a vision of a looser but stronger UK. Labour is uniquely able to both understand this vision, and to make it happen. In the Conservatives, Labour has an opponent which cannot countenance the prospect of a looser UK. And in the SNP, the party has an opponent which, self-evidently, does not wish to see a stronger UK.

Labour should model its position on that of the Coalition Avenir Quebec in Canada. Informally, their guiding principle is that you do not have to love Canada, but you do not have to leave it either. A similar guiding principle for Labour – you don’t have to love the UK, but you don’t have to leave it either – would be an optimal foundation from which to create complementary policy.

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It is hardly like Labour has not been in this position before, with the responsibility of remodelling the UK in order to hold it together. They should view this as a completion of the job; as a way to strengthen the UK through decentralisation.

For sure, that should include a clear vision from Sir Keir for which further legislative and financial powers should be passed from Westminster to Holyrood. However, as important is a clear vision from Mr Sarwar for which legislative and financial powers should be passed from Holyrood to Scotland’s local authorities.

A conversation with one of his predecessors, Lord McConnell, who has recently been active on the promotion of directly elected mayors and other passings of power to a local level, would not go amiss.

All of its current and future voters can get with this programme; everyone will have a raft to cling to.

I would observe that, at the moment, Labour has placed the constitution in the ‘too difficult’ box. They need to take it out. If they do not go out and grab these soft nationalist voters, the yellow wall will, more or less, stand.