Mahinda Rajapaksa has suffered a major blow to his campaign to get re-elected as Sri Lanka's president.
Chandrika Kumaratunga, one of the most senior members of his Sri Lanka Freedom Party (SLFP), on Sunday threw her weight behind General Sarath Fonseka, Rajapaksa's chief rival.
Kumaratunga, who served as president from 1994 to 2005 before being succeeded by Rajapaksa, is the daughter of the late founder of the SLFP, Solomon Bandaranaike.
Endorsing Fonseka on Sunday, she said: "Our party has deteriorated in recent years and I see an opportunity to revive it through a change of the present culture.
"I took the decision to end four years of silence as I am deeply concerned about the violence, intimidation and corruption."
Urging her supporters to vote for Fonseka, Kumaratunga said: "The prevailing violence and the breakdown in law and order poses a serious challenge to democracy, democratic institutions and values, as well as all the basic freedoms we cherish and have protected with great sacrifice over the centuries."
Saturday marked the last day of campaigning, but Rajapaksa and Fonseka, the two main architects of the defeat in May of the separatist Liberation Tigers of Tamil Tiger Eelam (LTTE) that ended a quarter-century of war, kept themselves in the public eye on Sunday.
Fonseka, Rajapaksa's former army chief turned main opposition candidate, visited Colombo's Kalaniya temple where he prayed with Buddhist monks before giving a news conference alongside Ranil Wickremesinghe, the former prime minister.
Rajapaksa also prayed with Buddhist monks and greeted supporters at an indoor stadium in the capital.
The streets of Colombo were calm on Sunday, but the opposition said the government planned to instigate violence to steal the vote.
Election-related violence has marred the campaign for weeks; five people have been killed and 78 wounded since December, according to a local group tracking the violence.
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Fonseka claimed that the government planned to stir up violence to keep voters from the ballot box on Tuesday.
Mangala Samaraweera, a former foreign minister who backs Fonseka, said: "In the face of inevitable defeat, the Rajapaksa regime, according to reliable information, seems to be conspiring to thwart the democratic process."
Fonseka and his allies pointed to alleged orders to the army, troop movements, plans to impede the election commissioner and preparations to disrupt the media as evidence of a coup plot.
Wickremesinghe described the government as "desperate" and said appeals were being made to the police and the armed forces of Sri Lanka not to carry out any illegal orders.
He said the opposition would launch street demonstrations if the vote was tainted.
Chandrapala Liyanage, Rajapaksa's spokesman, denied the allegations.
"The opposition is making baseless allegations to justify their defeat. We will have a peaceful election and all indications are that the president is comfortably ahead."
Sri Lanka's elections chief, Dayananda Dissanayake, said the authorities have taken all measures to prevent voting fraud, and urged security forces to ensure the safety of voters.
Both candidates have tried to cash in politically on their popularity among the Sinhalese majority for crushing the LTTE.
Some 80,000 to 100,000 people were believed to have been killed during the fighting, as the LTTE sought an independent state for the ethnic Tamil minority in the country's north and east.
But with the presidential race believed to be tight, the Tamil vote could be crucial and Rajapaksa and Fonseka have also courted the Tamil minority who make up about 18 per cent of the population.