POPULAR depictions of the fall of the Roman Empire conjure scenes of closing time at Glasgow’s Bonkers Show Bar. It’s not known if Quentin Tarantino ever visited the boisterous Hope Street nightspot but his cult vampire flick, From Dusk till Dawn made it seem as though he had.

Hollywood and a cast of populist historians would have you believe that the Vandals and the Visigoths were able to walk in, virtually unopposed, to wreck Rome because its leaders by then had become so vitiated by moral degradation that they were unable to lift a finger. As they were lolling about on their couches, howling with the Valpolicella; painting pornographic murals and taking liberties with the slaves and the horses the barbarian hordes simply helped themselves and the most powerful empire the world has ever seen duly crumbled.

The great American historian and philosopher Will Durant was somewhat more circumspect in his analysis of Rome’s decline but he too hinted at a bacchanal getting out of hand. In "Caesar and Christ", written in 1944, he observed: “A great civilisation is not conquered from without until it has destroyed itself within.”

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If you substitute the SNP for Rome in Durant’s famous judgment some of the forces that undermined that great empire have also lately become apparent in Scotland’s governing party. We might not yet be seeing the demise of the SNP but if the wider Yes movement fails to wrest control away from its fatally compromised leadership then they can kiss independence goodbye.

Two opinion polls, published yesterday in Scotland on Sunday and The Sunday Times have indicated a significant fall in support for independence following Nicola Sturgeon’s testimony last Wednesday. Doubtless, others over the next few weeks will produce sunnier numbers. Much more worryingly for supporters of independence though, are some of the details of the Sunday Times Panelbase poll. It suggests that the virtually-guaranteed SNP majority at May’s Holyrood elections may not be quite so secure after all. It also suggests that Scottish voters may not be quite as enchanted by Ms Sturgeon’s performance in front of the Holyrood committee as her cheerleaders in the party and the media have been.

Commentators and party loyalists have become so transfixed by the human drama of Salmond versus Sturgeon that they are overlooking what it also reveals about the deeper malaise that afflicts the leadership of this party: an all-consuming desperation to hang on to power at whatever cost to what remains of its soul.

Mr Salmond was tried last year in the highest court in the land and found to be innocent of each of the 13 charges brought against him. Nevertheless, his successor in her entirely unconvincing eight-hour testimony repeatedly sought to ensure that the focus was on his conduct and not that of her administration.

As well she might. When the Government you lead is revealed repeatedly to have subverted the work of a parliamentary committee and to have humiliated its own legal advisors by withholding information from them you are forced to make a choice: to be entirely honest or to shift the focus of attention elsewhere. Lamentably, Ms Sturgeon and her party apparatchiks chose the latter.

The First Minister was singularly unable to refute many of the substantiated charges laid at her door. One of those who corroborated the central ones around the dates of when Ms Sturgeon first became aware of the complaints made against her predecessor is Geoff Aberdein. A former chief of staff to Alex Salmond, Mr Aberdein is a formidable political operator respected across all political parties for his integrity and professionalism. He also claimed he was told the name of one of the complainers, weeks before the First Minister said she knew about any complaints.

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Now, it’s been reported that not only was he asked to change his account of the leak but that if he didn’t it would damage the career of the government official involved. This points to an administration that has become so drunk on power that anything is now deemed acceptable in removing all obstacles that might threaten its dominion.

These tactics are wretchedly familiar to all those others now considered to be traitors and who have been menaced simply for not bending the knee to the identity cult which has hollowed out this party. By pandering to this tiny, but deeply intolerant and misogynistic faction, Ms Sturgeon and all those shamelessly seeking preferment avoid the much more difficult task of levelling up in those communities still struggling in the SNP’s long, unchallenged tenure.

Owing to the hopelessness of the main opposition parties during this period the SNP have become lazy, arrogant and self-indulgent. This has recently been observed in the way it has gerrymandered party lists so that an assortment of leadership loyalists, some of them truly hopeless and transparently careerist, could secure top rating.

Some of Nicola Sturgeon’s most fervent party acolytes have become so caught up in her cult of personality that they are actually trying to make a case for an egregious lack of transparency around these placings. You still can’t quite believe either that many of these – following their leader’s example – are still unable to locate the spark of humanity that would permit them to support some of their female colleagues who recently faced violent intimidation.

Their barely-concealed contempt for those who participate in those big Saturday marches has also been apparent. They dismiss them as “those Common Weal types” and give the impression that the rank and file are something to avoid getting on the soles of their shoes but which might nevertheless be required to help fertilize the soil later on.

Yet, now it’s those Common Weal types – those who want to free the SNP from the cult of personality and replace it with actual policies – who must now act to redeem the independence movement. They must hope that it’s not too late, for the threat to their Holyrood dominance – and thus to a second referendum – comes just a few weeks before election campaigning begins.

It really shouldn’t have come to this. That it has is almost entirely down to the egos of an entitled inner sanctum who had convinced themselves they could do no wrong.

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