Horacio Cartes leads in the polls for Sunday’s presidential elections in Paraguay. Campaign posters in the landlocked nation’s capital, Asuncion, show his beaming face above a slogan declaring “a new direction” for the country. But detractors of the millionaire Colorado Party candidate offer a different vision: a man mixed up in a host of illicit activities, including drug trafficking. A man who represents big business and corruption.

Mr Cartes is one of Paraguay’s most influential figures. Over the past two decades the businessman has built up a powerful empire. He owns some 25 companies, spanning the drinks industry, meat production and tobacco, employing thousands. Since 2001, he has also been president of Libertad football club. But damning allegations continue to swirl.

“Cartes has bought farms, a drinks bottling company and a football team,” says Chiqui Avalos, author of The Other Side of HC, an exposé of the leader. “He has also bought a political party and now he might be able to buy a country. This would be terrible.”

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The most serious smear against the 56-year-old involves drug trafficking and contraband cigarettes. In 2011, WikiLeaks cables originating from the US embassy in Buenos Aires placed him at the centre of a drugs and money-laundering network operating out of the lawless frontier with Argentina and Brazil. Mr Cartes has publicly denied the allegations and says he has received assurances from the embassy that the US Drugs Enforcement Agency and Bureau of Alcohol, Tobacco and Firearms are conducting no investigations against him, something the cables allege.

But the drugs scandals are nothing new. In 2000, drugs enforcement officers intercepted a small plane on one of Mr Cartes’s farms carrying a cargo of of cocaine and marijuana. Mr Cartes said that an unknown plane landing on his property had nothing to do with him.

“When it comes to drug trafficking, Horacio has made it clear what his position is,” says Julio Velazquez, a Colorado senator standing for re-election tomorrow. “There’s no concrete allegation against him. Horacio has investments in the US. Do you think the Americans would allow a narco to bring money into their country?”

Mr Cartes has spent millions of dollars financing his campaign. A political outsider, he only joined the Colorado Party in 2009, the same year he added his name to the electoral register, meaning he had never voted in a Paraguayan election before. In the past, potential Colorado presidential candidates needed to have been party members for 10 years; Mr Cartes had the law overturned.

No expense has been spared bringing in top advisers to oversee his campaign. The focus has been Mr Cartes’s success as a businessman, an idea underlined by Senator Velazquez who mentions his “vision for investment”.

“Cartes obeyed his advisers for much of his campaign,” explains author Chiqui Avalos. “He didn’t open his mouth. The campaign was focused on the Cartes Group, his business interests and the work he’s given people. But in the last two months he has begun giving his own talks – and the results have been terrifying.”

The Colorado leader’s recent ability to put his foot in his own mouth has led the left-wing presidential candidate Mario Ferreiro to state that “a silent Cartes was a mystery. Talking he’s a disaster”. His most polemical statements have centred on his admiration for the traditional Paraguayan family while comparing the LGBT community to “monkeys”. Earlier in the month he said he would “shoot myself in the b*****ks” if he were to discover a son who wanted to marry another man.

“Cartes’s comments are completely immoral,” Sergio Lopez, head of SomosGay, a LGBT organisation based in Asuncion, tells The Independent.

The most recent scandal, however, has been allegations of a secret offshore account in the Cook Islands run by the bank he owns, Amambay Trust, illegal since 2003 according to Paraguayan law. Senator Velazquez says the story is dirt-digging from the opposition and that although the bank was created “there was no movement of cash within it”. So why was it created in the first place? “I’m not in a position to answer that,” he replies.

Mr Cartes isn’t quite the runaway victor he once was, due to the scandals that have stuck to him and a recent alliance the second-placed Liberal candidate Efrain Alegre has made with another party. A poll gave him 47.6 per cent of the vote while Mr Alegre trailed with 32.5 per cent. Some commentators says the margin has now shrunk.

But the Colorado Party is a colossal machine and doesn’t get knocked down easily. Before the leftist former priest Fernando Lugo came to power in 2008, the Colorados had enjoyed an uninterrupted spell of 60 years in power, including the controversial dictatorship of Alfredo Stroessner, Latin America’s longest serving despot. To this day, more people are card-carrying Colorado Party members than any other movement.

“The Colorado Party created this strong patronage system,” says Antonio Soljancic, a social scientist at the Autonomous University of Asuncion. “So in order to get a job you had to show you were a party member. The problem Paraguay has is that, although Stroessner disappeared from the political map, he left a legacy that no one has tried to bury.” For Chiqui Avalos there is still fear surrounding the Colorado Party, making it impossible for him to find publishers for his book. “I think many people will be voting for Cartes out of fear more than anything else,” he says.