IN 2011 Alex Salmond led his party to an “impossible” absolute majority in the Scottish Parliament elections – overriding all the checks and balances created by the architects of Holyrood. Now, four years, one indyref and one leader later, Nicola Sturgeon is at it again. According to pollsters Ipsos Mori, the SNP is set to win every single Scottish seat in the General Election – a result that should be impossible with Britain’s unfair and archaic first-past-the-post system.

And there’s more. Earlier this week, the SNP louped two other electoral hurdles when a Survation poll showed higher support among women (52.5 per cent) than men (50 per cent) for the first time – astonishing when you remember the gender gap that existed nine short months ago – and a breach of the psychological 50 per cent barrier.

It’s heady, heady stuff and prompts elation and apprehension in equal measure.

Since we’re (mostly) Scots, let’s take the apprehension first.

If the final weekend of the campaign is filled with crowing triumphalism by any part of the SNP or Yes movement, or if Nicola Sturgeon is found to have secretly joined the Tory party at university like Nick Clegg – Scotland’s 20 to 30 per cent of undecided voters could yet take a scunner and vote Labour or Lib Dem in Highland seats. It’s not very likely, I’ll grant you, but rock-solid leads have been squandered before by smugness and premature celebrations. For 50-somethings like myself, the memory of Neil Kinnock’s o’er early victory party in 1992 is impossible to erase.

Eighteen months in the preparation, the Sheffield rally was attended by 10,000 Labour Party members, reportedly cost £100,000 to stage and culminated in Kinnock being flown in by helicopter. Packed with sound and light performances on stage and celebrity endorsements on video screens, the shadow cabinet paraded to the stage through the crowd with politicians being introduced as “The next Home Secretary” and “The next Prime Minister”. Finally a tired and emotional Labour leader took the podium and repeatedly shouted “We’re alright!” Toe-curling was too small a word for it. Almost overnight Labour’s lead evaporated and three lost General Elections became four.

And of course, more recently, there’s the memory of “that” 51 per cent poll a week before the independence vote.

Mercifully though, next Thursday doesn’t look likely to be a repeat of either scenario.

Unlike that single rogue result, which helped rouse Better Together, the SNP has been sitting pretty for months at 45 per cent support or more.

And everyone in politics learned from Neil Kinnock’s disastrous and presumptuous display. Such cocky razzamatazz might work in America but in Presbyterian Scotland it is the kiss of death. Nicola Sturgeon is less inclined to acts of provocation or flamboyance than her predecessor, so there’s little chance of dangerous triumphalism before votes are cast – and maybe even afterwards. 50 per cent may vote SNP on May 7 – but 50 per cent may not. Scoffing and taunting defeated candidates may feel good to some but it’s an indulgence I imagine the First Minister will not allow herself.

The other anxieties are really imponderables since the whole of British politics is about to enter completely uncharted territory. Sure, we’ve had a minority Westminster government before. But not one that says it will refuse to deal in any way with its most likely supporters.

If Ed Miliband is to be believed he intends to snub SNP MPs – if given the chance to form a minority government – and will refuse to negotiate any aspect of policy direction with them. Of course treating the SNP like pariahs may seem to make sense as Ed tries to hang on to swithering English voters. But in practice, could a new minority Prime Minister really behave as if democratically elected MPs were untouchables? Especially when Scottish voters will have so consciously changed the Westminster voting patterns of several centuries to send tough-talking SNP candidates south to represent them?

The Survation poll showed

48 per cent of voters completely or mostly trust Nicola Sturgeon but only 14 per cent feel the same about Jim Murphy.

If Labour want to reduce that trust rating to a permanent minus figure, they need only ignore the verdict of the Scottish electorate after May 7. Because a sea-change has taken place here in the last two years.

A macho wee country has taken a woman to its heart as leader. A nation that used to defer to Westminster politicians looks set to flex its collective muscle in the most gloriously un-choreographed display of like-mindedness since every Tory MP was voted out in 1997.

Of course there will be choppy waters ahead.

Change won’t come quickly or easily at Westminster. The SNP leadership will find itself stretched, there will be a challenge to beef up land reform and community empowerment legislation in Holyrood and the need to elbow into power at Westminster, while ultimately wanting out of it.

And yet one thing looks clear.

Jim Murphy can’t stop the SNP now – only smugness and complacency can.