It has become a cliché that since Scotland’s indyref the “winners” and “losers” have changed places. Yes campaigners who were in tears on September 19^th are today mobilised as never before. Back then the SNP had 25,000 members; now it has 92,000, almost one in 50 of Scottish adults. In time, this influx of activists may become Nicola Sturgeon’s biggest headache, but for the moment they are happy to serve as foot soldiers in a national-popular party which is 20 points ahead of Labour in the polls and, after next May, could hold the balance of power at Westminster. Other pro-independence parties and groups – the Scottish Greens, the Radical Independence Campaign and Women for Independence (which also demands Independence for Women) – are also riding high.

In stark contrast, six weeks ago Scottish Labour (current membership 13,500) was plunged into acrimonious disarray by the surprise resignation of Johann Lamont, the party’s sixth leader in 14 years. To be fair, the three candidates vying to replace her – Sarah Boyack MSP, Neil Lindlay MSP and Jim Murphy MP – have all gone out of their way to appeal for party unity, whoever wins the contest. But this cannot disguise the pattern of fault-lines exposed by Lamont’s decision to quit. Hitherto a rather dour, cautious politician, in her resignation statement, she sounded a bitter, heartfelt note when, in words that might have been scripted by Alex Salmond, she complained that her Westminster colleagues had treated the Scottish party as a “branch office”. This charge was directed less at Ed Miliband than at Scottish Labour MPs, who have always had a condescending attitude to Holyrood, regarding Westminster as the cockpit of UK politics with themselves as top cocks.

Earlier this year, when the Scottish party was debating its “forward offer” of extra powers to be devolved to the Scottish parliament in the event of a No vote, the MPs blocked Lamont’s desire for Holyrood to be given full control over income tax, threatening to boycott the special conference at which the offer was to be approved. The result was a messy, incoherent compromise that pleased no one and provided critics with an easy target. Ironically, the party’s representatives in the Smith Commission charged with transforming the last-ditch, pre-referendum “vow” made by the three pro-Union parties from pig-in-a-poke into a coherent draft bill, have just reluctantly agreed to fall into line with the Conservatives and Lib Dems by accepting the full devolution of income tax powers, worth £10.8 billion a year in tax revenue. This U-turn is still opposed by Gordon Brown and Alistair Darling, but they are both stepping down as MPs next May.

Besides the rift at the top, Scottish Labour is divided between left and right, while relations between party and unions are far from cordial, as became evident, for example, in last year’s machinations surrounding the selection of a candidate in Falkirk to replace the disgraced former Labour MP, Eric Joyce. But the party’s most serious fracture is that its voters are split three ways on the question of independence. Around a third of them voted Yes in the referendum, while a significant minority of the rest favour Home Rule (an aim which the party shared in common with the Liberals until the Great Depression of the 1930s, the pressures of total war in the 1940s and the establishment of the welfare state after the war led to the centralisation of the British state). Hardly surprising then that Nicola Sturgeon is urging Labour supporters to “lend” the SNP their votes in next May’s general election.

Yet the front-runner in the race to become Scottish Labour leader is the candidate least well qualified to lift the party out of crisis and meet the existential challenge posed by the SNP. As a former New Labour minister and proven street fighter, Jim Murphy enjoys the backing of his parliamentary colleagues. But by the same token, he epitomises the problem of Westminster domination. Nor will his record of support for the Iraq War and for keeping the Trident submarine fleet endear him to most Scots. What Labour desperately needs is not someone to keep banging the drum for a moribund political union, but a leader who opposes the break-up of Britain by proposing a new constitutional settlement. By analogy with the pluralist, inclusive character of Scottish nationalism, we might describe such a project as civic unionist.

Labour’s jittery, uncertain response to Ukip in England reflects an underlying failure to recognise that loss of faith in the UK’s political institutions is just as potent a source of popular discontent as falling living standards and job insecurity. There are, to be sure, no easy solutions. But it is no use parking the issues in a post-election constitutional convention. Labour must grasp the nettle of constitutional reform, reconnecting with its own historic roots and reaching out to nationalists, Greens and, indeed, federalists in all parties by embracing the idea of Home Rule All Round.