Chavez tapped Maduro as his successor before succumbing to cancer, leaving him as the flag-bearer of a political movement that radically transformed this oil-rich nation of 29 million people. Maduro built his campaign on vows to continue the "21st century socialism" that made Chavez a hero to millions but deeply divided the country.
"We're all going in the bus of the fatherland, which has a driver," Maduro said upon launching his election campaign from the late president's childhood home. "Here he is, Chavez's driver!" Read: Chavez heir Maduro wins Venezuela's presidency
But Chavez's endorsement and the outpouring of grief that shook the nation when he died from cancer on March 5 were not enough to propel Maduro to an easy victory in Sunday's election.
Venezuela's election authority declared Maduro the winner with just 50.7% of the vote in a cliffhanger, but opposition candidate Henrique Capriles said he would not respect the outcome without a full recount.
Acting Venezuelan President Nicolas Maduro waves to supporters as he leaves after voting for the successor to the late President Hugo Chavez, in Caracas. Reuters
If the result stands, Maduro will have to set his own route as he steers through a difficult economic environment and potential divisions within the diverse coalition that Chavez built and held together with a mix of astute power politics and unmatched charisma.
His first weeks in office will offer a glimpse of his own vision for Venezuela, which he concealed during his tenure as foreign minister and vice president by parroting the utopian but vitriolic rhetoric of his "Supreme Commander."
True to form, Maduro dedicated the election to Chavez in his victory speech, holding up a photo of the late president superimposed over an image of Jesus Christ.
He now faces a complex economic panorama of rising inflation and slowing growth, internecine jostling within the fractious ruling Socialist Party, and growing complaints about one of the highest rates of violent crime in the world.
Venezuela's newly elected President Nicolas Maduro celebrates his victory after the official results of the presidential elections were announced, at the Miraflores Palace in Caracas, Venezuela. AP
Maduro, a burly 50-year-old, is known to favor dialogue and has developed a reputation as a moderate who could help Chavismo - as Chavez's political movement is called - shed some of its sectarian hostility and rigid economic doctrine.
He is rumored to be considering dismantling cumbersome economic controls and pondering a rapprochement with Washington.
Still, speculation about his policies remain little more than guesswork by "Kremlinologists" trying to read between the lines of gushing and hagiographic eulogies of his former boss. Read: Venezuela votes to defend the legacy of Chavez
Opposition supporters react as they hear the official presidential elections results in Caracas, Venezuela. Hugo Chavez's hand-picked successor, Nicolas Maduro, won a razor-thin victory in the special presidential election. AP
Perhaps fittingly, Maduro once played guitar in a rock band called Enigma.
His best-known trait remains his prominent mustache, which supporters - women and men alike - have taken to imitating by pasting strips of black foam on their upper lips, calling it the "Mustache of the Fatherland."
Jesus And The Pharisees
During the campaign, Maduro called himself and cabinet ministers "apostles of Chavez" and derided the opposition as "Pharisees" in reference to the Jewish sect that the Bible's New Testament says clashed with Jesus.
He told one story of exchanging whistles with a bird while praying at a shrine in Chavez's hometown, leaving him convinced he had been visited by the late president's spirit.
Chavista militants and government supporters wait for presidential election results outside the Miraflores Palace in Caracas, Venezuela. AP
That was ridiculed by his detractors and mercilessly exploited by cartoonists who mocked the tale using the Twitter bird icon and images from the popular video game Angry Birds.
Maduro later appeared on stage at one rally wearing a straw hat adorned with a model bird, and released dozens of the winged creatures at a huge demonstration to close his campaign.
He also warned his adversaries they could succumb to a curse known as "Macarapana" linked to a 16th-century massacre of native tribes by Spanish colonial troops.
"If anyone among the people votes against Nicolas Maduro, he is voting against himself, and the curse of Macarapana is falling on him," he told a crowd in Amazonas state, on the remote jungle frontier with Colombia and Brazil.
Hours before Chavez's death, Maduro accused "imperialist" enemies of infecting the president with cancer - the kind of headline-grabbing claims against powerful foes that Chavez often used to rally supporters during his 14 years of tumultuous rule.
Opposition critics lampoon Maduro as a poor imitation of Chavez and deride his speeches as parroting the late president without the charm or independent thought.
"Nicolas' biggest weakness is that it seems he doesn't even exist, the only thing you see in the campaign is the image of the president (Chavez) ... Nicolas is just not up to it," Capriles told Reuters in an interview during the campaign.
After Sunday's contested election, Capriles said Maduro had become an "illegitimate" leader, a sign of the stormy relations that the new president is likely to have with the opposition.
Little is known about Maduro's life before he joined Chavez's cause shortly after the then-lieutenant colonel burst onto Venezuela's political scene with a failed coup. Read: Venezuela's President is a Sai Baba devotee
One blogger said that scouring through dozens of texts about politics and leftist social movements of the late 1980s and early 1990s turned up at best fleeting references to Maduro.
"Nearly every personal and intimate detail (about Chavez) was publicly known," wrote a contributor to the website panfletonegro.com who goes by Edgar B.
"But about Nicolas Maduro, nothing, a complete and total informational vacuum ... In some places he's mentioned almost as a footnote, but in most cases he doesn't appear anywhere. What was our president up to all those years?"
In 1992, when Chavez was jailed for the failed coup that made him famous, Maduro took to the streets to demand his release and visited him in prison.
Maduro's long-time partner, Cilia Flores, led the legal team that helped get Chavez freed within two years. The two have long been seen as a power couple in the government.
Venezuela's interim President Nicolas Maduro flashes a victory sign in Caracas, Venezuela. AP
A rabble-rousing legislator on the frontline of the successful effort to defeat a brief coup against Chavez in 2002, Maduro rose to head the National Assembly, swapping the blue jeans and plaid shirts of a union leader for sharp suits.
Even in his smarter attire, however, Maduro used to elbow through reporters to get to the appetizer table before presidential news conferences.
One of his offices featured a portrait of the late Indian spiritual guru Sai Baba, whom he and Flores visited in 2005.
As foreign minister, Maduro had a fairly dull image as a loyalist who never diverted from Chavez's line. Still, those who know him say this is no reason to underestimate him.
"He has always followed Chavez unconditionally but not because he's not smart enough to do otherwise," said Vladimir Villegas, Venezuela's former ambassador to Mexico who later joined the opposition.