Gordon Brown will learn early tomorrow whether Labour has held on in the Glasgow East by-election, with the outcome remaining on a knife-edge.

Labour strategists believe that good weather today will encourage core supporters in the previously rock-solid Labour seat to come out and vote, thus helping the party to stave off defeat at the hands of the Scottish National Party. The forecast for the Glasgow area is, however, decidedly mixed, with the prospect of some sunny spells alternating with showers.

Labour is defending a 13,507 majority and, after the debacle of the Crewe & Nantwich by-election in May and losing its deposit in Henley last month, a rebuff from the voters in one of the party's Scottish fortresses would be highly damaging.

There are hopes of a higher-than-expected turnout, although this is based largely on a 73 per cent return rate for postal votes. Although none of the parties believes that turnout will match the 48 per cent at the 2005 general election, they think that there is a chance it will be just under 40 per cent, given the massive media interest.

Another key factor will be the relative success of Labour and the SNP in ferrying their pledged voters to the polling stations from the time they open at 7am. For both parties, military-style operations will swing into action involving hundreds of party activists armed with details of which voters need transport and when they intend going to the polling stations.

Labour is planning a 5am letter-drop at 10,000 addresses in the constituency urging voters to back their candidate, Margaret Curran, as “a fighter for the East End”. The operation will be repeated at 6pm. The leaflet will also point out that Mrs Curran is third on the ballot paper, to avoid confusion with Frances Curran, the Scottish Socialist Party candidate. Labour will also target its leaflets at supermarkets, railway stations and car parks throughout the day.

The SNP will have 600 activists in the constituency and 200 vehicles offering transport to polling stations. The Nationalists also plan a last-minute leaflet campaign.

The SNP says it has made about 60,000 telephone calls to voters during the campaign. Labour's tally of telephone calls is about 20,000. Both parties say that they have visited 40,000 households.

Yesterday saw the final shots fired in the short campaign, which has been downbeat in spite of the potential importance of the outcome.

Mrs Curran for the first time launched what could be seen as a personal attack on Alex Salmond,

the First Minister and SNP leader, accusing him of wanting to talk about himself all the time. “I think a lot of people would thank me if I got to wipe the smile off his face,” she said.

Mrs Curran mounted her final push for support employing a soapbox in the manner of John Major when he led the Conservatives to a narrow victory in the 1992 general election. Almost harking back to the way that political campaigns used to be conducted, she delivered a stump speech standing on the box outside a bingo hall. An upbeat Ms Curran, Labour's fourth choice after three senior party figures rejected the candidacy, told campaign workers: “I promised that the Labour fightback was about to start. The Labour fightback is under way and we are on our way.”

Labour has fought a localised campaign, concentrating on constituency issues and barely mentioning Mr Brown. Its opponents have concentrated on the Westminster Government's travails on the economy, and attacking the Prime Minister for not showing up in the campaign.

Mr Salmond, who has been campaigning in Glasgow East almost daily, raised the stakes this week by predicting that a political “earthquake” was about to hit Labour in the seat. Asked whether he still believed that, he said: “We believe we are neck and neck. The earthquake is coming and will arrive on time and on schedule ... the impact of an SNP victory would be totally extraordinary.”

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