The former Labour cabinet minister George Rob­ertson spoke for many when he predicted that devolution would "kill nationalism stone dead". But what he and others failed to anticipate was that nationalist politicians would adapt best to the new political landscape. Of no one is this more true than the Scottish National Party (SNP) leader, Alex Salmond, who is on course to win a second term as First Minister of Scotland after a remarkable comeback by the SNP.

Largely unnoticed by the English media, the SNP has overturned a double-digit Labour poll lead and is likely to become the single largest party after the 5 May Holyrood general election. A YouGov survey published on 24 April put the SNP on 45 per cent in the constituency vote, with Labour trailing on just 32 per cent. If repeated at the election, these figures would leave Mr Salmond just nine seats short of an overall majority. The first SNP victory in 2007 ended Labour's hegemonic grip on Scottish politics. A second, as Rob Brown writes on page 30, could transform the SNP into the "natural party of devolved government".

The surge in support for the SNP is not the result of any increase in anti-Union sentiment. Instead, it reflects Mr Salmond's considerable personal appeal and the popularity of the social-democratic agenda he has pursued. While George Osborne rolls back the frontiers of the welfare state in England, the SNP leader is rolling them forward in Scotland. Since taking office, his government has abolished NHS prescription charges, frozen council tax and introduced free school meals for all pupils aged five to eight. At the same time, the SNP has maintained its commitment to free care for the elderly and to free university education for all Scottish students. Such policies may be fiscally reckless - the funding gap is estimated to be £975m - but they are politically canny. Mr Salmond, a formidable politician, has deftly positioned his party to the left of Labour and will be rewarded on 5 May.

Labour's disastrous Scottish campaign poses grave questions, not just for the party's leader in Scotland, Iain Gray, but also Ed Miliband. In his recent address to Labour's Scottish conference, Mr Miliband explicitly called for voters to turn the election into a referendum on the Westminster coalition. He urged the public to use the contest to give Labour "the best chance of stopping it going to the full term". That the people appear unwilling to do so suggests that he has badly misjudged the mood in Scotland after one term of SNP governance.

In a feverish attempt to prevent defeat, Labour has belatedly changed tack, warning that voters now "stand on the edge" of triggering the break-up of the Union. Yet a poll published in the Scottish Sunday Mail on 24 April showed that just 33 per cent would vote in favour of independence, were a referendum to be held. It is precisely for this reason that many no longer fear voting for Mr Salmond's party. In practice, as the former SNP deputy leader Jim Sillars has written, his party has softened its support for independence in an attempt to win votes "from all and sundry", including Unionists. At some point in the future, the constitutional status of the UK, which is now neither a unitary nor a federal state, will need to be resolved. But there is little to suggest a second SNP victory would result in independence for Scotland.

Should Labour lose to the SNP on election day, the party will be denied what Mr Miliband rightly identified as a platform to set out a "real alternative" to the coalition government. Moreover, if, as seems likely, the voters reject the Alternative Vote in the electoral reform referendum, two significant opportunities to undermine the Conservatives will have been missed. The prospect of an emboldened Tory party fighting the next election under first-past-the-post, having redrawn the constituency boundaries in its favour, is a reminder that Labour will not return to power simply by riding a wave of anti-cuts discontent. Unless the party offers a far clearer vision of the kind of society and economy it wishes to create, there is every danger of this being a new Conservative century.