IF the latest opinion polls are anything to go by, it looks like Labour are going to win the next Westminster election in Scotland. The percentage points might be narrow – Labour and SNP support each hovering around one-third – but the merciless logic of the first-past-the-post electoral system, from which the SNP have benefitted since 2015, might now swing the result, in terms of seats, the other way.

This loss of support is mostly undeserved. By any objective analysis, the SNP have done a reasonably good job, in difficult circumstances, of running a devolved administration.

Scotland of course still has a long way to go before reaching the normal levels of ­socio-economic development of a north-western European nation, but real progress has been made. Take child poverty, for example. Deep, inter-generational, child poverty has long been a national disgrace. But the SNP’s practical, pragmatic, brand of social democracy has at least started to turn things around.

Free school meals, Scottish Child Payments, Baby Boxes, Best Start Grants and the expansion of free childcare show what can be done, even with limited fiscal powers, if the political will is there.

The electorate should reward those ­achievements, and be wary of voting for a ­Labour Party that threaten to undo them.

Yet promoting the interests of Scotland ­within the devolved framework is only the secondary aim of the SNP. Their primary aim is to achieve independence. It is belief in independence that unites and mobilises the party.

On that issue, the SNP have a problem. ­Despite the party’s long run of electoral ­dominance, we are still no closer to independence than we were on the grim morning of September 19, 2014. This is despite Brexit, despite Boris, ­despite the ­calamities of the British state, ­despite ­everything that “Project Fear” threatened ­coming true ­anyway.

What most harmed the SNP’s credibility on independence was taking the referendum case to the UK Supreme Court. Even casual ­observers of the Supreme Court in recent years must have noted the court’s high ­doctrine of parliamentary sovereignty and the slim chances of success.

The National: Humza Yousaf

One might reasonably argue that the ­referendum bill would have ended up in the Supreme Court anyway, sooner or later, but the SNP should have been prepared for that ­institutional stand-off, mobilising people in the words of the supporters of the 1832 Reform Act: “The bill, the whole bill, and nothing but the bill.”

The backup plan was to use a ­parliamentary majority as a mandate to negotiate for ­independence. In principle, that should make sense. The Union has traditionally been ­understood – by Unionists as well as ­nationalists – as a union of consent.

A majority in either parliament should ­suffice to signal the withdrawal of that consent. ­Before the Scottish Parliament was established, it was accepted, as a matter of convention, that the election of a pro-independence majority of Scottish MPs would be enough to trigger ­independence. The Colonial Office in the 20th century generally accepted that the election of a pro-independence majority in the devolved legislature would be a sufficient mandate for a managed transition to independence to begin.

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However, it is hard for the SNP and the ­wider independence movement to stand on those claims today, when we have had a majority in both parliaments, but sat on our hands for so long. Why did we not do it in 2015, instead of getting caught up in the Westminster games?

Besides, whichever trigger we use, a ­referendum or a parliamentary majority, the main question is the same – does Scotland ­really have the right and ability to decide our own ­constitutional future, or are we to continue ­under Westminster’s sovereignty?

The Claim of Right is an authoritative and legitimate articulation, which has been signed by the Scottish Constitutional Convention and endorsed by both parliaments, of the central concept on which public authority in Scotland rests – the sovereignty of the people.

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It declares a fundamental antithesis between the people of Scotland and the Westminster Parliament. If the people of Scotland have the right to determine our own constitutional future, then it logically follows that the Westminster Parliament has no such right.

The independence debate is not about whether the people of Scotland should have sovereignty. Sovereignty is a given, a non-negotiable starting point. The debate is about whether Scotland, in the exercise of our sovereignty, wishes to remain in a Union with England, Wales, and Northern Ireland, or to withdraw from that Union.

To deny and – if necessary – to defy the ­sovereignty of Westminster takes boldness, steadfastness and intransigence. It means being willing to take the initiative and escalate the political pressure on the British State.

If the SNP are not willing to do that, then no amount of devolved good governance will save them.

The SNP are an independence party or they are nothing. They need to prove they are serious about ­taking the steps independence will entail.