Our last pre-poll guest blog comes from the Greens’ co-convenor Patrick Harvie, standing again at the top of the party’s list in Glasgow.

So the end is in sight. After a long campaign and, for me, a tough four years of trying to make an constructive impact with a parliamentary group of just two, we’re on the eve of the 2011 Holyrood election.

Much comment has been made of the dramatic turnaround in the polls, from a clear Labour lead, through a period when they were roughly neck and neck with the SNP, to some apparently commanding poll leads for the Nationalists.

Few people would say that Labour has helped itself much over the last couple of months. Their campaign has been lacking in just about every quality which could possibly inspire people to put them back into government.

Of course nothing is certain until the votes are counted, but if the polls are right about the scale of the SNP lead (and the LibDem collapse) then the SNP might just be faced with some far more profound choices than they had to make in the last session at Holyrood.

In 2007 the SNP were given an extraordinary opportunity: their first chance to form a government. I supported many of the things they’ve done with that opportunity, and I opposed many others. But crucially they proved that minority government was viable in Scotland.

They did so in what should have been a very weak position. Fully 18 seats short of a majority, they had to find support week after week either from Labour (which was rare) or from at least two other parties. Their success rate owes a great deal to the abilities and straightforwardness of Bruce Crawford, but it wasn’t easy and on many issues it proved impossible.

But if the polls are to be believed the next five years could see a much stronger minority position for the SNP. If they lead a government which needs only the support of any one other party to form a majority, they will have a far more powerful role. But with that power would come responsibility. They would find themselves faced with a genuine choice of political direction, which arguably they have not had in the last session. So the second question in this election is about the balance of power, and the Tories have made it very clear that they hope to exert greater control over the next government.

Most SNP activists, I’m pretty sure, are resolute in their opposition to any formal coalition with the Conservatives, and the party’s rules against such a deal still stand. But even those activists must recognise that the government’s strongest informal relationship has been with Annabel in the blue corner. It has covered motions both meaningful and symbolic, legislation and amendments on many issues, all budgets, and policy development too… even if the Tories gave little sign of interest in the actual delivery of changes to drugs policy once the press releases were out.

Faced with the option of maintaining and deepening that relationship, or cutting it off to open up new possibilities in the progressive ground of Scottish politics, what will they do?

There can be no doubt that on charisma, on face recognition, and in a personality contest for the “top job”, the SNP are leading the field. But if the SNP do find themselves with a choice over who to work with in the next Parliament, they will be challenged to do what they as well as Labour have so far failed to do, and construct a serious response to the economic crisis which acknowledges the failure of the deregulated free market model which has been dominant for so long. The lack of such a response from political parties which style themselves the “mainstream centre-left” has been dismal, and it has been left to the likes of UK Uncut, the Robin Hood Tax campaign, and many in the trades union movement to begin the task.

If the SNP are interested in being part of that response, or even leading it in Scotland, they must look to an alternative balance of power in Holyrood. There is simply no prospect that it can be done by a government which is reliant on the votes of the UK Coalition parties to get through its programme.

So the change at the top of the polls over recent weeks is important, of course. But the change lower down could be even more crucial. It could open up the chance for a long term realignment in our politics, and a greater unity of purpose between centre-left and radical movements, if the will exists to see that happen. Or it could leave us with a de facto centre-right government in Scotland despite the overwhelming number of voters whose votes and opinions lean leftward.