Senior sources in both the Scottish National Party and Scottish Labour are predicting a narrow nationalist victory in the Glenrothes by-election, by perhaps 1,000 or maybe 1,500 votes.

Labour has been making up lost ground against the SNP, but - if the predictions are right - the party will say that they just didn't have enough time to close the enormous gap that the nationalists had opened up.

If you look back to early September, there were widespread predictions that the SNP would take Glenrothes by between 3,000 and 5,000 votes.

Much has happened since then, with the financial crisis and Gordon Brown's political comeback. Labour will say that they have made huge inroads into the SNP vote but that they have simply run out of time.

The nationalists have run a very good campaign, keeping it very, very simple. While Labour has been saying that Gordon Brown is the man to lead the way through the financial crisis, the SNP has been pointing out that it was on Brown's watch, as Chancellor and Prime Minister, that the financial problems first began to appear.

What is surprising to me is that Labour has decided otherwise to run a very, very local campaign, based on the SNP's record in running the local council and the parliament, majoring on home care charges and education costs. They did not attempt to fight it on the dangers of independence, which - given that Scotland's two biggest banks have been in so much trouble and forced to accept a bailout by the UK government - seems to me a missed opportunity that Labour may come to regret come 2am when the result is in.

Others will say that running a campaign on the constitutional issue risks boring people, as only one third of Scots favour breaking up the UK and independence isn't really on the agenda at the moment.

And the SNP's ability to get their vote out will be crucial again today. We saw when they won another massive victory earlier this summer in Glasgow East how effective they were at getting their voters out, whereas Labour had some major problems in that direction. Any repeat of those problems in Glenrothes could be the final blow for Labour's chances.

Labour has been getting more pessimistic as the big day approaches. A loss is going to be a blow for the party, which has thrown the kitchen sink at the Glenrothes contest, with two visits from the Prime Minister, visits from the Chancellor and John Prescott, and with Sarah Brown apparently taking up permanent camp in the constituency. By comparison, Labour's Glasgow East by-election campaign was very low key.

It will also be a personal blow for the Prime Minister and may sap energy from the Brown bounce, as this is very much Mr Brown's backyard. His home in Scotland lies only four miles away from Glenrothes.

The SNP seem to be defying political gravity at the moment, with few signs yet that they are losing popularity 18 months after they came to power. It is turning into an almost interminable political honeymoon.

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