THINK of all the effort: the 2014 referendum, the rows over Brexit, the calls for a second independence vote in 2016 and Every Single Year thereafter, the Supreme Court case, the briefing papers, the street rallies, the clenched fists and the gritted teeth. And for what exactly? The SNP is two points ahead of where it was in 2014. Two. Lousy. Points.

I must say even I’m a bit surprised given the number of times the SNP has seemed to be gathering momentum. The 2015 General Election. Post-Brexit. Post-Boris. And, most recently, the days after the Supreme Court verdict on a second referendum. Moments like those encourage Yes campaigners, always an excitable bunch, to wheel out metaphors about soaring rockets only to wheel them back in a few weeks later.

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The latest sign that the rocket is heading for re-entry was the polling at the weekend for The Sunday Times. What it showed was that support for the SNP, for independence and, perhaps most crucially, for Nicola Sturgeon herself have all fallen sharply. The metaphor Sir John Curtice, the polling guru, chose to use was relentless battering; it’s taken its toll, he said.

Here’s the nitty-gritty of what the poll said: in the space of a month, SNP support for the Holyrood constituency vote has fallen from 50% to 44%, and from 40% to 36% in the regional vote. The poll also shows the party’s Westminster support has fallen from 43% to 42% and that Ms Sturgeon’s approval rating has slipped into negative, from +7 to -4. As for independence, backing for that is down from 53% to 47% – as I say, a mere two points ahead of where it was at the 2014 referendum.

All the usual caveats apply. It’s one poll. It excludes the don’t-knows. And there have been ups and downs before. The shift in opinion may also be down to one of those short-lived factors that cause volatility before settling down again. We saw it with the Supreme Court ruling and we may be seeing it again this time with the sex offender who changed gender identity and was sent to a women’s prison. People get angry, but people also forget, and we go back roughly to where we were.

However, a couple of significant things are worth noting, the first of which relates to what isn’t in the poll rather than what is. What there isn’t in there is any kind of sign of an SNP breakaway to the consistent level of support that will make a difference, which many people (including plenty in the SNP) agree is around 60%. Ms Sturgeon’s other problem is she’s set a much lower threshold for her “de-facto referendum” (50%) but even that appears to be sliding away from her.

The other point worth talking about is the SNP’s reaction to the poll. Keith Brown, the deputy leader, said in response to it that Scotland was rich in resources, and independence meant an escape from Westminster control. In other words, it’s the same-old-same-old. Doesn’t he realise though that if your arguments aren’t getting you closer to the destination, you should think about a different route?

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Granted, the SNP has been recalibrating a bit in recent months by trying to manage expectations of an independence panacea. You can also hear the beep-beep of the reversing alarm as they start to back away from the de-facto idea. But what’s lacking from them is any kind of nuance or humility. Mr Brown says about the latest poll that the SNP is still the most popular party, but his colleague Joanna Cherry was closer to the truth with her remark that the leadership should eat some humble pie before more damage is done.

The greater point is that, whatever the fluctuations of a point or two in the polls, the SNP still needs to convince and win over the reasonable middle and perhaps they will allow me to give them a bit of advice on that (I know they value it): take a look at what the former Green MSP Robin Harper has been saying recently. Listen carefully to his points about Holyrood, devolution, and co-operation because I think there are seeds in there of a way forward for everyone.

Inevitably, what Mr Harper has to say hasn’t won him popularity in his old party although he should probably wear that as a badge of honour alongside his trademark colourful scarf because it’s pretty reasonable stuff. Devolution should go further. The Scottish Government has centralised too much. The committee system at Holyrood is useless. Given the huge problems all countries face, nations should co-operate as much as possible. We shouldn’t abandon a democratic system simply because it has been mis-used by populists. And finally: what Scottish politics really needs is a few years of peace.

Obviously, Scottish nationalists would disagree with Mr Harper’s tilt against independence and the SNP hard-core might disagree with the rest of it. But the SNP will have to tackle these central ideas if they are ever to make progress with the reasonable middle, and there’s no reason why they can’t do some of that while also arguing for independence in the longer term.

For instance: they could support further devolution to councils and possibly mayors; it could go some way to tackling the SNP monoculture which is so off-putting to many Scots. The same with government majorities on Holyrood committees. Create more of a sense that the system in Scotland prioritises diversity and robust questioning of the government and more voters might therefore feel comfortable about supporting the SNP and even independence, knowing there are proper checks and balances.

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The same applies to Mr Harper’s other points. He points out that our democratic system has in recent years been mis-used by populists, leading to Brexit for example, but he also points out this is not an argument for abandoning the system entirely. A lot of Scots get this and Keith Brown needs to understand it too if he’s not to waste his time with constant reductive arguments about Westminster as it currently is.

Which leaves Mr Harper’s other big point, which is that countries should co-operate as much as possible. Obviously, the SNP believe the current co-operation in the UK is too much but there’s no reason why, in arguing their case, they cannot emphasis what kind of co-operation there will still be after independence.

What they could say more of is this: we’ll always be neighbours; we’ll always share a similar culture; our economies will always be mutually dependent. So admit it. Admit pure independence isn’t possible. Then tell us, honestly, and humbly, how you think the post-independence co-operation will work. That way, you might just get more people to listen.