Vagates between about tied and up to fifteen points down, and has for years.
Drops through that floor whenever "devo max" is also offered as an option in the same poll - even if not directly as an alternative but as a separate question.
^^^^^
This
Essentially I'd say there's a 'hard' 35% for, 45% against and 20% either way depedning on mood or the wording of the question. Having a national debate about independence will of course shift this; Salmond is banking on being able to win over the 20%. It's not entirely impossible for him to do as he will be leading the YES campaign (at least the public face) but the NO campaign will be the three unionist parties and business groups. Cameron can't lead it and the Scots have a tendency of doing the opposite of what a Tory says. Miliband of course can't lead anything.
If you end up with
several NO campaigns against Salmond being Salmond then it's going to be a walk in the park for the YES vote.