Electors in the last constituency to vote in Ghana's presidential run-off delivered a further blow on Friday to the ruling party, which was already trailing narrowly in the election and boycotted the final ballot.
Opposition leader John Atta Mills and the ruling party's Nana Akufo-Addo are vying to succeed outgoing President John Kufuor as the West African country prepares to start producing crude oil in 2010.
The winner is due to be announced on Saturday after the Electoral Commission has examined appeals from both sides over alleged irregularities in last Sunday's run-off.
That vote was so close that Tain's 53,000 voters were left to decide the outcome, raising tensions over a vote seen as a chance to bolster Africa's battered democratic credentials after flawed and bloody polls in Zimbabwe and Kenya.
Before Friday's vote, Mills, of the National Democratic Congress (NDC), led with 50.13 percent of votes, ahead of Akufo-Addo, of the ruling New Patriotic Party (NPP), on 49.87 percent. Barely 23,000 votes separated the two candidates.
As expected, provisional results announced on Joy FM radio from Tain extended Mills's national lead after Akufo-Addo's NPP boycotted Friday's vote citing security concerns.
Mills picked up 19,566 votes compared to just 2,035 for Akufo-Addo, according to results announced by the district returning officer on Joy FM radio. The rural constituency, voted late due to problems which prevented it voting in last Sunday's run-off.
Even before the NPP boycott in Tain, Mills was favorite to win Friday's ballot, in a cocoa growing region, and to take the presidency after his NDC overturned the ruling NPP's majority in parliament in a simultaneous legislative election on December 7.
Mills led in Tain then, so Akufo-Addo would have required a huge swing in Tain to win the national vote.
Akufo-Addo has refused to concede defeat and the NPP has appealed results from other regions, citing irregularities.
But Electoral Commission chief Kwadwo Afari-Gyan told Reuters he would announce results on Saturday, leaving little time for any major revision of the results announced on Tuesday.
"I am declaring the results tomorrow at 11 a.m. (6 a.m. ET)" he said.
The Electoral Commission is considering appeals from both parties, which each accuse the other's supporters of violence and irregularities in Sunday's ballot. International and local monitors said voting was generally free and orderly.
"It significantly raises the stakes, it significantly raises tensions ... (but) I'm not sure Ghana would necessarily descend into chaos or major instability. There is no historical precedent for that," said Rolake Akinola, analyst at consultancy Control Risks in London.
The NPP, which continues to govern until Kufuor steps down, applied on Thursday for a court order to prevent the Electoral Commission publishing more results, and sought to have the Tain vote delayed. But a lawyer for the party told Joy FM radio on Friday both cases had been withdrawn.
Earlier, youths in NPP T-shirts crammed into buses belonging to state-owned Metro Mass Transport and cruised round Tain's district capital, Nsawkaw, chanting "No Vote" at people queuing at polling stations.
Hundreds of soldiers and police have been deployed in Tain to ensure calm, searching vehicles entering Nsawkaw for weapons.
Despite the potential for a protracted legal dispute over the poll, Kufuor said in a statement it was important to stick to the timetable for him to hand over the presidency on January 7.
"I therefore urge all stakeholders to yield to the authority of the electoral commissioner when he declares the result. Any outstanding issue may be settled later by due process," he said.
Under Kufuor's rule Ghana, the world's No. 2 cocoa grower and Africa's second biggest gold miner, has attracted increasing foreign investment thanks in part to its political stability.