By Fernan Gonzalez-Torres
BBC Latin America analyst
Daniel Ortega ruled Nicaragua from 1979 to 1990. Now, after losing three presidential elections, he is running again as the candidate for the Sandinista Front in Sunday's elections.
The fact that opinion polls put him ahead in the race is causing alarm in Washington.
After three electoral losses, Mr Ortega is hoping for a comeback
For the Bush administration, Mr Ortega represents the old left in Latin America and a man with close links to President Fidel Castro of Cuba and the Venezuelan President, Hugo Chavez.
While Mr Ortega was in power in the 1980s, the US saw him as a threat to stability in Central America.
In Guatemala and El Salvador, leftist guerrillas were fighting US-backed governments. The fear in Washington was that the Sandinistas would support them militarily.
Washington tried to undermine Mr Ortega's government by training and arming disaffected groups that came to be known as "contras". President Ronald Reagan even ordered for mines to be laid in Nicaragua's harbours.
The government of the Sandinista Front of National Liberation (Sandinista comes from Augusto Cesar Sandino, a nationalist leader who fought against US military presence in Nicaragua between 1927 and 1933), implemented land reform and made efforts to improve living conditions for the poor and to promote gender equality.
Although many people benefited from the changes brought by the Sandinistas, the movement also polarised Nicaraguan society.
Nicaragua's business community was deeply suspicious of Mr Ortega's government, believing it would follow President Castro's policies of nationalisation in Cuba.
Daniel Ortega: Sandinista Front
Eduardo Montealgre: Liberal Alliance
Jose Rizo: Constitutionalist Liberal Party
Edmundo Jarquin Calderon: Sandinista Renewal Movement
And, in an overwhelmingly Roman Catholic country, many Nicaraguans felt alienated by the tension between the Sandinistas and the Catholic Church.
There was also widespread rejection of compulsory military service, as many young men died in the war against the Contras.
In the presidential elections of 1990, Mr Ortega was unexpectedly defeated by Violeta Barrios de Chamorro, the widow of a journalist killed by the Somoza regime. The opinion polls had predicted a victory for the Sandinistas.
Although Mr Ortega failed to be elected in successive elections in 1996 and 2001, he has never given up his attempts to return to power.
Mr Ortega knows that he has to convince a large number of Nicaraguans to get the 40% of the vote required by law to be declared outright winner.
If he fails to reach that percentage, he needs at least 35% of the vote and a 5% margin over the nearest other candidate.
The Sandinista leader, now 61, has made unlikely alliances with some of the groups that fought against his government in the 1980s.
His running mate, banker and former Contra leader Jaime Morales, is the original owner of the house where Mr Ortega and his wife Rosario now live.
It was confiscated by the Sandinistas when they were in power.
Mr Ortega has dropped the red and black colours of the Sandinista flag in favour of pink and has asked for forgiveness for what he describes as his mistakes.
He often talks about his Christian beliefs - and he and his wife were married in church after many years of living together.
Recently, the Sandinista Front voted in Congress in favour of a total ban of abortion.
Many critics say that the transformation of Ortega and his party amounts to nothing more than political opportunism.
Image or substance, the truth is that if he is elected, he is unlikely to return to the revolutionary path of his government in the 1980s.