Nicola Sturgeon: The moments that led to the First Minister's resignation

• ITV Border's Political Editor Peter McMahon examines the resignation of Scottish First Minister Nicola Sturgeon

She did not use these exact words, but in her resignation statement today Nicola Sturgeon effectively told her party, her government and the Scottish people: "I am the problem, not the solution."

Politicians of all stripes find it very difficult to admit to faults or mistakes. They always have to be right. Admitting failure is seen as a weakness, which will be exploited by their opponents.

So in a brutal business where self-belief is everything, there must have been a long dark night, or nights, of the soul for one of Scotland's most self-assured politicians to come to this conclusion.

In her statement at her Bute House official residence the First Minister maintained that there was majority support for Scotland leaving the UK, for her core belief in independence.

She added: "But that support needs to be solidified - and it needs to grow further if our independent Scotland is to have the best possible foundation. To achieve that we must reach across the divide in Scottish politics.

"And my judgment now is that a new leader will be better able to do this. Someone about whom the mind of almost everyone in the country is not already made up, for better or worse. 

"Someone who is not subject to quite the same polarised opinions, fair or unfair, as I now am."

Nicola Sturgeon announcing her resignation as Scottish First Minister at Bute House, Edinburgh on Wednesday 15 February

It was quite a moment. There is little doubt that Nicola Sturgeon has become a divisive figure. Loved by her party and by (most) independence supporters, loathed by many (not all) Unionists.

To nationalists there will have been a logic to her admission. Those who take a thoughtful view of the quest for independence accept they do need to reach out to 'soft indy supporters'.

A First Minister who admits herself she divides opinion would have difficulty doing that.

Those who support Scotland remaining in the UK will generally take a different view. For them it is the cause of independence itself which divides. You are either for or against. For them it is a divisive creed, whoever leads the SNP.

But there is more to this resignation than this simple self-realisation. It has not just been on independence that Nicola Sturgeon has divided Scotland. 

Leaving aside the complexity and subtleties of the issue - that could take up several more blogs - her plans to reform gender identity have divided opinion, and polls suggest she has not been able to take the voters with her.

But her difficulties go well beyond gender reform. As we said on Representing Border last week, "When sorrows come, they come not single spies, but in battalions".

Her government had not yet come to resemble a Shakespearean tragedy but in recent months the First Minister had not had her troubles to seek.   

A health service struggling to cope with post pandemic pressures, teachers on strike, a failure to build new ferries for CalMac, the promise to close the attainment gap in schools unmet, councils crying foul over funding, pledges on road building jettisoned, questions over SNP funding, the deposit return scheme in doubt.

The list could be extended and more extensive but there was also her plan to turn the next UK election into a 'de-facto referendum' on independence, following the rejection of a plan for a second independence vote by Westminster.

Her suggestion met with open criticism from within her party, something which in the 15 years in power was very, very rare. There was talk the First Minister might not even get her way. All of this would have been unthinkable just a few years ago.

Remember, when she took over from her now former friend and mentor Alex Salmond in the wake of the 2014 referendum defeat, she was the first rock star politician. Even though the 'Yes' side had lost she packed out huge venues making the case again for independence. It was as if 'Yes' had won and 'No' had lost.

At the last Holyrood election, she came within an inch of securing an overall majority, which is very hard to do under the proportional election system.

Nicola Sturgeon was unchallenged and seemingly unchallengeable within her party and out with it as the opposition made very little impact. 

Then came the pandemic in which her communication skills came to the fore. Though we now know that many of the outcomes - positive and negative - were the same in Scotland as the rest of the UK, she was seen to provide calm reassuring, decisive leadership in sharp contrast to the way Boris Johnson was perceived.

But now, only a couple of years on from that, her fortunes and that of her party are in decline. Those difficult policy issues piling up, the recent polls suggesting less support for independence than there was in 2014, dissent and unease in the SNP ranks.

And despite having as recently as last month assured ITV Border and many others that she had a long time to go yet, it is clear all of this was weighing heavily on Nicola Sturgeon's mind.

Now that mind is made up. She has shocked many in her party who cannot imagine life without her. She has fired the starting gun on what could be a divisive (that word again) leadership race centred on the independence strategy.

And she has given hope to her opponents who, whatever they may have said in public, know that Ms Sturgeon was a formidable political opponent who will be replaced by a leader relatively unknown to the public. We should, of course, judge politicians by their achievements.

Ms Sturgeon can rightly claim policies like the Scottish child payment have made Scotland more equal, and progressive. She can say she was always in touch with Scots in supporting the EU and opposing Brexit. She can claim much of the credit for the SNP being in government for 15 years, which is remarkable in modern politics.

But on her core belief, that of independence, Ms Sturgeon leaves high office with that goal - her greatest goal, the goal above all she aspired to - unfulfilled. And looking unlikely to happen in the near future.

Enoch Powell once said that all political careers end in failure. Whatever her other achievements, judged on the issue of independence, that dictum will have to apply to Nicola Sturgeon, too.

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