One of the biggest tasks Maduro will likely face is attempting to hold together a diverse movement that includes radical leftists, moderates and many current and former military officers.
Analysts have speculated that differences might emerge between factions led by Maduro and Diosdado Cabello, the influential National Assembly president who is thought to wield power within the military. But thus far both men have denied such divisions and vowed to remain united.
After Chavez's Dec. 11 cancer surgery, Maduro stepped up his public appearances to fill the void, providing regular updates on the president's condition, calling for unity among allies and lambasting the opposition.
Maduro also showed how he could attempt to continue Chavez's socialist-inspired project. Speaking at one December rally, he vowed in vague terms to maintain policies that have angered the country's leading business federation, Fedecamaras, which was long at odds with the president.
"We aren't going to give dollars to Fedecamaras. What we're going to give them is pains, headaches with this Bolivarian Revolution," Maduro shouted, his voice hoarse. "I swear to you ... we're never going to betray the people of Venezuela!"
Chavez's deteriorating health led him on Dec. 8 to announce Maduro as his chosen successor. He said that if his illness prevented him from being sworn in on Jan. 10, government supporters should rally around Maduro and elect him president.
Maduro is expected to keep promoting programs such as free medical clinics staffed by Cuban doctors and subsidized food stores, which have endeared the president with the country's vast numbers of poor. Maduro has vowed to block a return to past policies that he said had benefited the wealthy.
"Our people will never again see the bourgeoisie plundering this country," Maduro said, adding, "Better to be dead than traitors to the people and to Chavez!"
That loyalty made Maduro a logical choice, political observers said.
"Maduro combines two characteristics that influenced Chavez in his decision to designate him as successor: first, his loyalty to the party leadership, and second, his positions in favor of popular measures," such as social programs for the poor, said Steve Ellner, a political scientist at Venezuela's University of Oriente.
In his youth, Maduro drove a bus for the Caracas Metro transit system and later became a union leader.
It's unclear when Maduro and Chavez first met. But Chavez is thought to have first gotten to know Maduro in the 1980s, when Chavez was a lieutenant colonel and began a clandestine movement of disgruntled military officers that eventually carried out a failed coup attempt in 1992. Chavez was jailed on military rebellion charges and then released in 1994 when he was pardoned.
Maduro went on to become a leading member of Chavez's nascent political movement, growing closer to the budding politician and also getting to know Cilia Flores, who is now attorney general and was Chavez's defense attorney following his arrest for the 1992 coup attempt.
After Chavez was elected president in 1998, Maduro was selected to join a special assembly to draft a new constitution. He was later elected to the National Assembly and then became president of the legislature.
Maduro was named foreign minister in 2006 and oversaw international efforts such as consolidating the regional diplomatic blocs ALBA and Unasur, strengthening relations with countries such as Russia, Iran and China, and overseeing a rapprochement with U.S.-allied Colombia. He is thought to maintain close ties with Cuba's government.
Maduro "is perceived by Chavez as a negotiator with diplomatic skills who could potentially gather the support of the different factions and keep it united in the difficult months ahead," said Diego Moya-Ocampos, an analyst with the London-based consulting firm IHS Global Insight.
"Nevertheless, he is not necessarily perceived as such within all the top ranks of the ruling United Socialist Party of Venezuela and the armed forces," Moya-Ocampos added.
Jennifer McCoy, a political science professor at Georgia State University, described Maduro as an easygoing man who has shown a willingness to talk with government opponents.
"He's always been someone who is easy to talk to," said McCoy, director of the Americas program at the Carter Center, which helped the Organization of American States facilitate dialogue between the government and opposition after a 2002 coup that briefly ousted Chavez.
Maduro was always willing "to discuss the issues, and I think that's really important going forward for Venezuela," McCoy said.
Before Chavez underwent his latest operation in December, he explained why he had chosen Maduro:
"He's one of the young leaders with the greatest ability to continue, if I'm unable to God knows what he does if I'm unable to continue with his firm hand, with his gaze, with his heart of a man of the people, with his gift for people, with his intelligence, with the international recognition he's earned, with his leadership, leading the presidency."
Associated Press writers Fabiola Sanchez and Ian James contributed to this report.
Venezuelans in U.S. hopeful of change
Venezuelans living in the United States are reacting with cautious optimism that there will be change in their homeland following President Hugo Chavez's death.
In the Miami suburb of Doral, Venezuelans watched on television as the country's vice president, Nicolas Maduro, announced Chavez had died Tuesday. At a popular restaurant, one person cheered at the news, but the rest watched quietly and refrained from any celebration.
Doral has the largest concentration of Venezuelans in the U.S. Dora's mayor and police chief prepared a security and contingency plan in the event of Chavez's death. Many Venezuelans are expected to gather at restaurants and meeting spots in Miami, though few people immediately showed up.
There are nearly 190,000 Venezuelans in the United States. Many are strongly anti-Chavez.