For a country that in five weeks could be taking a significant step towards leaving the 300-year Union with the rest of the United Kingdom, Scotland appears remarkably restrained.

The streets are not filled with protesters demanding independence and there is no obvious upsurge of nationalistic sentiment but, as the Populus poll for The Times indicates today, a political earthquake is taking place north of the border. For the first time in almost 50 years, Labour, according to our poll, is about to lose an election in Scotland. Devolution is about to deliver the kind of electoral blow to Labour in Scotland that these five decades of rule from Westminster could not.

While the rest of Britain could flit promiscuously between parties, Scotland was always loyal to Labour. Even when Mrs Thatcher was in her pomp and laying waste to political enemies across the rest of Britain, the Scots remained unimpressed and dutifully returned a majority of Labour MPs.

Labour’s demise in a devolved Scotland cannot be laid wholly at the door of Jack McConnell, the Labour First Minister. True, he has not been the most inspiring of political leaders and has lacked any real presence, but his coalition administration, along with the Liberal Democrats, has wrought some improvement in public services and brought about modest economic growth. The one real political risk Mr McConnell took when he introduced a ban on smoking in public places grabbed the right kind of headlines and has been a success.

The worm eating away at Labour support in Scotland, however, is not Scottish. Rather, as Labour strategists now admit privately, the problem is a prime minister widely perceived as past his sell-by date and irredeemably associated in the minds of voters with an unending debacle in Iraq and the scandal of cash for honours. Add deep Scottish opposition to the renewal of Trident on the Clyde and, as one Labour insider put it: “We are fighting against a tide. The Nats are winning because they’re not Labour.”

Mr Blair’s devolution legacy, it seems, will be a loosening of the ties that bind Scotland to England. Mr Brown’s devolution inheritance will be to have his right to rule in his own Scottish backyard challenged again and again by a nationalist party in power in Scotland.

On the evidence of this poll, it will now take a major gaffe by the nationalists and their leader, Alex Salmond, not to emerge early on May 4 as the largest party in the Scottish Parliament.

Mr Salmond has been allowed to fight the guerrilla-style campaign at which he is adept. When Labour thought last week that it had an open goal on SNP plans for a local income tax, Mr Salmond simply moved the goalposts and returned to his favourite theme: the alleged failings of the Prime Minister. Mr Salmond has even felt comfortable enough to take up “independence for England” as a theme and to speculate on the benefits of an independence-lite “social union” (shared monarchy, shared currency, shared interests).

Mr Salmond will also know, however, that he is not there yet. The poll proves that support for Scottish separation is still a minority pursuit, with only just over one in four Scots supporting it. If the SNP holds its cherished referendum on independence in 2010, it would, on these figures, lose it easily.

When the dust has settled on the probable May 3 result, Mr Salmond as first minister could elect to rule in minority in Edinburgh or attempt a majority coalition with the Liberal Democrats. The Lib Dems say without hesitation that they would never countenance a coalition allowing a referendum on Scottish independence but, given what has happened in Stormont these past few days, “never” can be a flexible word in politics.

In all this, Labour and Mr Brown as prime minister (and indeed David Cameron) will be largely spectators. Who said devolution was boring?

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