Support for the Union, as things stand, significantly outweighs that for full independence, but support for increased powers in turn outweighs the status quo.
The unionist parties in Scotland - or as I like to describe them, the Unionist Underground (thanks to a certain Mr Gray and a takeaway for the idea) - seem hell bent on toppling Alex Salmond. To date, the most they've managed is a small flesh wound when Alex tried to cover up information using the courts (and he's playing with fire over Europe in a similar fashion).
They thinking that by removing Salmond, the SNP's dream of independence will be over. That may be a false assumption. It would take a major scandal to topple him, and he's been around long enough that any skeletons in the closet would have appeared by now. But Sturgeon and Russell could carry the party provided Alex Neil keeps his mouth shut.
In addition to this, the Unionist Underground have opposed nearly every SNP policy and bill just through sheer bloody-mindness. And people have seen this. Where is the effective opposition? You don't necessarily need a leader with great oratory skills and confidence - there are those who thing Big Eck is a bit too smug - but you most certainly need a coherent and disciplined opposition.
Their cause is not helped by the current Westminster government, made up of one and a bit parties, neither of whom achieved anything much in Scotland. Then you have a Labour leader who appears like a Tory who got off at the wrong political bus stop, and has little in common with Labour voters let alone Scotland.
So, like the Nationalists, the Unionists are unable to provide a convincing argument for their political aims and beliefs.