Labour went big on the earthquake metaphors after winning the Rutherglen and Hamilton West byelection with a 20% swing. It no doubt felt seismic and earth-shattering for the party after its troubles in Scotland for more than a decade and the seemingly unbreakable dominance of the Scottish National party. Having been the largest party in Scotland for half a century, with a Scottish prime minister, Gordon Brown, and chancellor, Alistair Darling, Labour had crashed to potential electoral oblivion with just one seat in the House of Commons by 2015. Rutherglen and Hamilton West is just a single seat on the outskirts of Glasgow – one that has swung repeatedly between Labour and SNP for the last 10 years – but its convincing return to Labour was a sign the party has renewed vigour under Anas Sarwar, who appears to be picking up switchers from SNP, Conservative and Lib Dem voters. It puts many other three-way marginals in play for Labour, and suggests it could be on course to hoover up many centre-ground votes at an election. With a crushing 58.6% vote share, Labour won in Rutherglen by shifting itself rightwards, closer to the political centre in Scotland. The party attacked the SNP for allowing councils to raise council tax rates, for a congestion charge mooted by SNP councillors to enter neighbouring Glasgow, and for suggestions income tax might go up again. What Starmer’s election strategists will be looking at now is whether a revival of the party’s fortunes in Scotland has enough clout to propel him into No 10 with a decent working majority. Prof Sir John Curtice, the University of Strathclyde elections expert, said a uniform swing on this scale could lead to Labour winning 42 of Scotland’s 59 seats. This would probably lead to a comfortable Starmer win at Westminster. He injected a note of caution, however, that there was still “uncertain” support for the Labour leader. There are also the usual caveats that lower turnout at a byelection – around 40% on Thursday – means it is difficult to draw wider conclusions; and Rutherglen had its own particular circumstances of being an election to replace an SNP politician, Margaret Ferrier, who was being booted out for breaching Covid rules. Labour insiders are similarly cautious about whether the party will sweep to victory across Scotland, from a base of just two MPs at the moment. They are optimistic of winning just over half of Scotland’s 59 seats but north of 40 seems a tall order. However, Labour strategists are taking great hope from the feeling that their party is not a toxic brand in Scotland any more – as it was in the post-referendum “tsunami” of 2015 when the party got crushed between independence backers opting for the SNP and unionists edging towards the Tories. Analysis by the Scottish Election Study has found that Labour’s reputation in Scotland has changed. It is now, in essence, the least disliked party; it attracts voters from the other major parties in a way it failed to do a decade ago. The SNP’s falling fortunes under Humza Yousaf after the departure of Nicola Sturgeon are another reason why voters are turning towards Labour. Opinium polling from the Tony Blair Institute, analysed by the pollster Peter Kellner, also found it was partly to do with voters looking for the answers to the cost of living crisis and crumbling public services, more than the independence question. Its report found that while support for independence had not gone away, there was a recognition across Scotland that it was currently a more remote prospect. Kellner said: “The next election will be fought on competence, not the constitution, meaning Scotland is very much in play for Labour.” In Rutherglen, Labour appeared to have gained unionist and independence backers alike, signalling questions over Scotland’s constitutional future are no longer so strongly determining votes at a national level. While Labour is right to be cautious about whether Rutherglen can be replicated in 40 more seats across Scotland, the party could not have hoped for a bigger electoral boost heading into this week’s annual conference in Liverpool. Michael Shanks, the party’s newest MP, will be paraded on the main stage to rapturous applause from delegates. And the path to No 10 for Starmer is looking clearer.