If opinion polls in Paraguay are correct, the 62-year reign of the world’s longest-serving ruling party will end on Sunday at the hands of a presidential novice.

The Asociación Nacional Republicana, known as the Colorados, has ruled this desperately poor and chronically corrupt country since 1946, through dictatorship and democracy. Now its freehold on power is threatened by a former Catholic bishop attempting to become president in his debut political campaign.

Fernando Lugo quit the Church in 2006, though Rome has refused his request for laicisation, and now leads an opposition alliance of 20 parties and political movements that have rallied to his candidacy.

Though his alliance’s programme includes plans to boost employment, clean up public life and implement land reform, his campaign essentially hangs on the promise of national renewal after decades of Colorado kleptocracy.

“These days a magical word is appearing in the north, south, east and west of Paraguay: cambio – change,” says the softly spoken 56-year-old politician, whose speeches still sound like the sermons he gave when bishop of the desperately poor region of San Pedro. “I believe the people are ready for a real change. I believe they are ready for a change not just in personal, parties, but a real structural change in Paraguay and its institutions,” he says.

Were he to win he would become the first opposition leader to come to power peacefully since Paraguay won independence from Spain in 1811.

This would make him the latest in a series of South American presidential firsts that so far this decade has already brought the first left-wing President in Brazil, the first woman President in Chile and the first indigenous President in Bolivia.

For months Mr Lugo has maintained a lead over the Colorado candidate, the former education secretary Blanca Ovelar, who is hampered by the backing of the current President, Nicanor Duarte Frutos. He is widely believed to be corrupt and polls show that he is Latin America’s most unpopular leader, with an approval rating around 15 per cent.

The third main candidate is Lino Oviedo, a former Colorado general with past ties to drug traffickers. He staged a failed coup in 1996 and many Paraguayans believe he was linked to the assassination of the country’s Vice-President in 1999 during an internal Colorado power struggle.

To blunt the Lugo phenomenon, the Colorados have tried to paint the former bishop as a left-wing radical who will imitate Hugo Chávez’s experiment in Venezuela. As Mr Lugo has maintained his lead in the polls his opponents have mounted a vicious smear campaign against him.

In February President Nicanor claimed that Mr Lugo’s supporters were behind a plot to poison him, and the Colorados have tried to link him to the 2004 kidnapping and subsequent murder of the daughter of a former president by a small group of left-wing extremists.

Colorado election posters have even portrayed their rival as a commander in the Colombian Marxist Farc guerrilla group.

On Tuesday President Nicanor claimed that agitators from Ecuador and Venezuela linked to the Lugo campaign were planning a wave of violence during Sunday’s vote – a claim widely denounced by the Opposition as an attempt to instil fear and dampen voter turnout, which is seen as the key to the opposition’s chances of winning a clear mandate.

Mr Lugo has brushed off the Government’s attempts to portray him as a leftist radical, calling himself “a person of the Centre who has a certain distance from Left and Right but with the capacity to unite both”.

His alliance includes Marxists and socialists but its biggest component is the main opposition party, the Liberals, which traditionally represents the elite and urban middle class. There are even dissident Colorado groups backing Mr Lugo.

“If I were more to the Left or more to the Right I wouldn’t be able to real-ise this convergence of so many parties and movements that at times are antagonistic,” he said.

Though the polls consistently point to a Lugo victory, many voters are still wary of writing off the Colorados. The party is notorious for electoral fraud and vote rigging, and incumbency has given it some built-in advantages.

The State is by far the biggest employer in Paraguay and getting a public sector job has for decades depended on loyalty to the Colorados. When family members are also counted, this has traditionally given the party around a third of the vote – vital in a country with a first-past-the-post system.

Power and poverty

— Nearly twice the size of the UK, Paraguay has a population of 6,831,000: 90 per cent are Catholic

— Low per capita income, blamed on corruption and poor infrastructure, has improved since 2003 as demand for, and prices of, commodities increased

— Paraguay sells much of the power from the Itaipu hydroelectricity plant on the border with Brazil, the largest in the world

— Human rights groups say that at least 900 people disappeared during the rule of Alfred Stroessner, in 1954-89, and thousands more were tortured. Stroessner fled Paraguay after being driven from power, and lived in luxury in Brazil until his death in 2006

— The best-known Paraguayan is probably the footballer Roque Luis Santa Cruz, who currently plays for Blackburn Rovers

Source: CIA World Factbook, agencies

Times Recommends

• Michael Jackson: Not the final chapter
• Indian Army spends10m rupees on golf buggies
• Sacha Baron Cohen forced to tone down Brüno