Polling has closed in the Glenrothes by-election on which much of Gordon Brown's political reputation is riding.
The result was expected to be close and there were early signs that the turnout could be low.
One unofficial estimate suggested it could be just 48% as rain came to the constituency on Thursday night at the end of a damp, cold and overcast day.
If that figure proves right, it would be 8% below the 2005 general election at which Labour's John MacDougall, whose death has prompted the by-election, had a majority of 10,664 over the SNP.
If Labour loses Glenrothes to the SNP it would be the party's Scottish second by-election defeat in less than four months after losing Glasgow East to the Nationalists.
Victory for the SNP would take their Westminster tally of MPs to eight - and would be a major blow for Mr Brown, who broke with tradition to campaign in Glenrothes.
Eight candidates are contesting the November 6 by-election: Morag Balfour (Scottish Socialist Party); Maurice Golden (Scottish Conservative and Unionist); Peter Grant (Scottish National Party); Louise McLeary (Solidarity - Tommy Sheridan); Jim Parker (Scottish Senior Citizens' Unity Party); Lindsay Roy (Scottish Labour Party); Kris Seunarine (Ukip); Harry Wills (Scottish Liberal Democrats).
