Venezuelan President Nicolás Maduro, in power since 2013 and running for a third term on July 28, is confident he is still the right man to lead the OPEC country, but Sunday's presidential election has attracted a level of voter enthusiasm for the opposition that could topple his regime.

Maduro's face looms large from posters plastered on street lamps, murals and advertisements along Caracas's major thoroughfares, with slogans urging people to vote for the president.

"Come rain, shine or lightning ... we're going to win by a landslide," he said in a recent broadcast on state television, shortly after reading out mock election results in which he notched "an irreversible victory." He has branded the opposition as "extreme right," and warned of a "bloodbath" if he loses, a comment that angered the president of neighbouring Brazil.

But part of the enthusiasm seen for the main opposition comes from his former supporters, the "Chavistas" who once turned out in droves for the party of Maduro and his late mentor Hugo Chávez, according to interviews Reuters carried out at opposition rallies and in cities around the country.

"We've spent 25 years supporting Chavistas with the hope that at some point they were going to straighten out the country's path, but every day is worse," said teacher Marina Perez at an opposition rally in Valencia. Her salary had not increased in two years, she said.

"Now there are two leaders who give us new inspiration," said Perez. "That's what we want: a change."

Yes, two leaders.

María Corina Machado — despite her popularity and her resounding two million vote victory in the opposition's primary — is not the opposition candidate. Venezuela's top court in January upheld a ban on the 56-year-old industrial engineer, that prevents her from holding public office.

She hasn't receded from view, instead thrown herself into campaigning for her replacement as the official candidate, former ambassador Edmundo González, drawing crowds that sometimes number in the thousands, according to attendees and images captured by media, with sometimes tearful attendees often giving them rosaries or other tokens.

Economic collapse, mass migration

Maduro, 61, has presided over an extended economic collapse in the once relatively affluent South American nation. Almost 82 per cent of Venezuelans live in poverty, with 53 per cent in extreme poverty, unable to buy even basic foodstuffs, a UN special rapporteur said in February after visiting the country.

Some 7.7 million migrants have left the country the past decade. Most of those have gone to Colombia, but an increase in migrants reaching the U.S. border has caused headaches in Washington, with Venezuela earlier this year refusing to accept deportations of migrants without valid asylum claims.

Years of mismanagement, falling oil prices and U.S. sanctions have all hurt crude output in Venezuela, but almost 60 per cent of the country's income is still set to come from oil in 2024, according to official figures.

Critics both at home and abroad say Maduro is a dictator who has jailed or persecuted political opponents, repeatedly and unfairly blocking opposition candidates from participating in elections.

States and many other Western countries consider Maduro's win in 2018 to be a sham. A Western effort the following year to coalesce support around Juan Guaidó did not lead to meaningful change.

Enthusiasm, but concerns about vote count

Machado and González have spoken at length of the need to reunite families amid the migrant crisis.

"When there is a rally what I see is joy, excitement, because the crowd hopes the country will change," said Darwin Mendoza, 27, a delivery driver in Aragua state.

Machado has characterized Maduro's government of being a "criminal mafia."

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González, 74, served as ambassador to Argentina between 1999 and 2002. In his first campaign appearance in May, González said he wants to build a country "where the president does not insult. A country where everyone belongs, leaving confrontation behind."

He brings his own lunch on the campaign trail, saying in a video on social media he wants to prevent any businesses that he patronizes being shut down. Several restaurants where González and Machado have stopped have later been shuttered, as have some hotels.

The opposition has warned that decisions by electoral authorities — from polling station staffing to the lay-out of the ballot — have been made with the intention of confusing voters and creating obstacles to a free election.

Along with Western governments, they will be watching intently to see if the election, to be held on the day of Chavez's birth, will be fairly administered with accurate results.