THERE is a film out next February called The Invisible Woman.

Based on the biography by Claire Tomalin, it is the story of Nelly Ternan and her relationship with Charles Dickens. As such, it should not be confused with the 1940 comedy of the same name, nor the predicament of Johann Lamont, Scottish Labour leader, who was revealed this week to be the invisible woman of the independence debate.

There were many fascinating findings to emerge from the TNS BMRB poll for The Herald. Some were to be expected, such as Prime Minister David Cameron scoring a "dislike" rating of 57%, putting him on a par with the winter vomiting virus for popularity. Nor was there much comfort for First Minister Alex Salmond and Deputy First Minister Nicola Sturgeon when it came to the female vote. Only 22% of women respondents liked Mr Salmond, with just 19% keen on Ms Sturgeon. Alistair Darling, Better Together leader, is similarly struggling to connect with women, with just 10% being partial to him.

But it was the finding on Johann Lamont that caused the most stir. Some 41% of the 1004 respondents did not have a Scooby as to the Scottish Labour leader's identity. Never mind liking or disliking her; many could not even pick her out of a line-up. She is the Keyser Soze among the usual suspects of Scottish politics, the Holmesian dog that does not bark, the Mrs Nobody whose face few ever see. One would think it had been two minutes, rather than two years, since she was elected leader. How can a politician be so invisible? And does it matter given the ensemble nature of the campaigns?

Pleading ignorance of politicians is a favourite pastime of the electorate, one much taken advantage of by TV crews on a slow news day. Take a bunch of photos out to the street and ask Joe and Josie Public to distinguish between the Defence Secretary and a hole in the ground, a deputy PM and a pineapple. It is a fine way to keep politicians grounded, and it reminds the media that not everyone lives in the same Westminster or Holyrood bubble.

Lamont as invisible woman remains a mystery, though, particularly given the Scottish electorate's apparent eagerness over the referendum. Scotland's Future, the Scottish Government's White Paper on independence, is now in its third reprint. Some 40,000 copies of the book-sized manifesto have been published and despatched. There are either tens of thousands of wonky tables out there, or the public is genuinely hungry for information.

Lamont's invisibility is even more peculiar when one considers the favourable impression she has so far made at First Minister's Questions. Drawing herself up to her full height of five feet something, she stands there majestically, as if on an invisible stairheid, ready to ask penetrating questions of this slick salesman who has turned up on her doorstep punting independence. Try to sell her a dodgy currency strategy? Pull a fast one over childcare plans? Play the fancy Dan over EU membership? On your way, son.

While this approach may play to those who would easily dismiss her as "a wee Glesga wumman", there are plenty more out there who reckon this very ordinariness is a huge part of her appeal. There are lots of wee Glesga women out there, and all have votes. Patronise them at your peril, boys.

Also in her favour is a distinctly Scottish and relatable hinterland. Before entering politics she was a teacher, a profession that holds a firm place in Scottish affections. Born in Glasgow, her parents were from Tiree, giving her one foot in the city and one foot in the islands. Not for her a Bullingdon background that has to be hidden. The roots of which she is so proud have informed her left of centre politics and made her a practical practitioner of the craft. "Now let's get started," was her rallying cry on being elected leader. While never going to give Obama anything to worry about as an orator, she had once again made a virtue out of her ordinariness.

She has been brave enough, too, to challenge the political consensus, as when she highlighted the cost to the genuinely disadvantaged of such universal benefits as free prescriptions and no tuition fees. It was a daring move for any Labour leader, particularly one faced with a Scottish Government so determinedly optimistic about Scotland's ability to pay for everything under an independent sun that its campaign theme tune might as well be "Roll out the (oil) barrel".

A final factor that should have been on Ms Lamont's side is that she is part of a Borgen moment in Scottish politics. Together with Ms Sturgeon and Ruth Davidson, the leader of the Scottish Conservatives, she has had more access to the spotlight than most Scottish women politicians have enjoyed.

Given all these advantages, why then does she remain the invisible woman? More pertinently, why is Mr Darling, rather than Ms Lamont, leading the Better Together campaign? The former Labour Chancellor is slowly but surely attracting critics, and not all of them are muttering Tories inside Downing Street. Some are muttering Tories outside Downing Street. Boris Johnson, the Mayor of London, though he made no mention of Mr Darling or anyone else by name, is not alone in wondering whether Scots are likely to respond badly to being "endlessly warned and hectored" about the dangers of independence instead of hearing a positive case for the Union.

Ms Lamont, it is true, has so far shown herself no more capable of making that case than Mr Darling, but a new approach would be more convincing if it was made by a fresher face.

Then again, Ms Lamont, for all her relative newness, has almost as much political baggage as Mr Darling. Both are products of Scotland's old Labour past, the past that was so convincingly rejected in 2011. As she said herself, Labour lost its way, lost its confidence, and in doing so lost Scotland.

Nor did she have a good Grangemouth. With so many other big beasts prowling the scene, in London and in Edinburgh, she all but disappeared from view. Mention of Grangemouth, moreover, leads inevitably to discussion of the Falkirk candidate selection fiasco and its aftermath. Though her displeasure was obvious, London soon made it clear that it was not minded to re-open the inquiry. When it came to keeping up appearances, London looked after itself. If it thought at all about the impact on Ms Lamont's standing as a leader, it did not do so for very long. Clearly, it was not just among Scottish survey participants that Ms Lamont was the invisible woman.

Invisibility is a condition that can be cured easily enough in the 24/7 media age. But Ms Lamont, like any other politician, needs something convincing to say. Like the rest of the No camp, she has gone suspiciously quiet on the matter of what else they are offering Scotland other than the status quo. The invisible woman needs to leave her Scottish Parliament comfort zone and get on the airwaves and out on the doorsteps, for those are the places where the fight will be won or lost.