HOWEVER unexpected the SNP’s loss of 21 seats was two years ago, the one consolation was that they hadn’t played any part in bringing that election about – they abstained on Theresa May’s motion for a snap poll, perhaps realising the only way they could go was down.

This time, they confidently expect to make gains, and on that assumption have taken decisive action to bring about the vote in December. Could another surprise result cause them to have regrets?

If the most recent Scottish opinion polls are to be believed, it’s unlikely. Although the 2017 result left the SNP vulnerable to heavy seat losses if there’s even a relatively small swing to Labour, polls have consistently suggested that the opposite will happen. A Panelbase poll earlier this month recorded an SNP lead over Labour of 20 percentage points – double what it was on polling day two years ago. If the election result is anything like that, the SNP can expect to practically wipe Labour out, with Ian Murray once again the last person standing as in 2015.

Even in his seat of Edinburgh South, there must be a question mark over what will happen if the large number of tactical anti-SNP votes he received in 2017 go elsewhere this time. The LibDems have a strong tradition in that constituency, and could perhaps entice many of Murray’s voters away with the clarity of their “stop Brexit” pitch.

The potential prize for the independence movement is enormous. Scottish Labour have been close to suffering a wipeout before, but not on the sub-20% share of the vote that recent polls have reported.

If their remaining voters look at a result of that type and cease to take them seriously as an electoral force, they could effectively be taken out of the game completely. That could mean in future elections the SNP will be practically unchallenged across large swathes of the central belt, and will have a clear run against the Tories or the LibDems in the more affluent or rural seats.

But how secure is that prize? On the basis of what happened in the 2017 campaign, we’d have to conclude it’s not very secure at all. Westminster elections are “away fixtures” for the SNP, and they will always be fighting an uphill battle against London-based parties who receive far more airtime during the official campaign period and who are perceived as the true contenders for power. The speed of the Corbyn bandwagon effect took the SNP totally by surprise two years ago, and brought back into play constituencies they had assumed were rock-solid.

There’s certainly no room for complacency over the coming weeks, because contrary to popular belief, lightning does sometimes strike twice.

Another concern is the possibility of a Britain-wide LibDem bandwagon caused by voters liking what they see of Jo Swinson in the televised leaders’ debates. It shouldn’t be forgotten how the polling situation was utterly transformed overnight after Nick Clegg’s strong performance in the first debate in 2010.

If an excitable media suddenly starts talking up the possibility of a LibDem government in the wake of a Swinson surge, Scottish voters could be inspired by the prospect of the pro-Remain MP for East Dunbartonshire becoming Prime Minister, and that could have unpredictable effects. At the moment, it’s very hard to see how the LibDems can do much more in Scotland than hold their four current seats and gain the ultra-marginal seat of North-East Fife from the SNP. But that could change if they start polling higher than 20%.

It would certainly be advisable for SNP supporters to stop salivating at the possibility of unseating Swinson in her own constituency. Remember that she won her seat very comfortably in 2017 at a time when the LibDems were on less than 7% of the vote across Scotland, and were 30 points behind the SNP.

With the traditional bonus that any new party leader can expect, it’s almost inevitable that she’ll be re-elected, and probably with an increased majority. The SNP are quite right to throw the kitchen sink at her, but the main purpose of that will be to lay down a marker and demonstrate that there aren’t any no-go areas for the party. The chances of dislodging any of the other three Scottish LibDem MPs also look remote.

Thankfully, it’s a very different story as far as the 13 Scottish Tory MPs are concerned – most or all of them are potentially vulnerable. This month’s Panelbase poll reported an SNP lead over the Tories of 18 points, constituting a 5% swing in the SNP’s favour since 2017. If that was the final result, it would see eight of the Tory seats fall. And if anything, Panelbase has painted a less optimistic picture for the SNP than other firms – a YouGov poll two months ago suggested the gap between SNP and Tory was 23 points, which would be enough to reduce the Tories to just three seats. Until a few weeks ago, it had looked as if some kind of informal pact with the Brexit Party might make life easier for the Tories, but as a result of Boris Johnson’s new deal with the EU, Nigel Farage is now determined to inflict as much damage as possible.

Ironically, the main effect in Scotland could be a reversal of the 2017 trend that caused some unionist commentators to triumphantly declare the campaign for a second independence referendum “dead”.

With a few caveats, then, it’s fair to say that the prospects for the SNP at the outset of this campaign look rosy. But will a strengthened SNP contingent in the Commons find itself largely impotent in the face of a powerful majority Tory government hellbent on denying a Section 30 order and delivering a Hard Brexit?

At the moment, the polls suggest that is the most likely outcome. But this will be a unique election, wholly dominated by Brexit, and it’s quite possible that the penny will start dropping for pro-EU voters that they have the numbers to defeat Boris Johnson with a bit to spare – but only if they coalesce in a more effective way than they are currently doing. They have a few weeks to crack that puzzle, and as countless recent elections and referendums across the world have proved, that’s more than enough time for the contest to be turned upside down.