Venezuelan President Hugo Chavez is one of the leading leftist figures in Latin America and one of the United States' most vocal critics, aligning himself with former Cuban President Fidel Castro and Iranian President Mahmoud Ahmadinejad.

With a win in Sunday's elections, the 58-year-old Chavez, who has been in power since 1999, will enter a fourth term in office and extend his presidency into 2019, or two full decades in power.

Read: Hugo Chavez wins re-election

When first elected on December 6, 1998, in a landslide, Chavez was at age 44 the youngest person in the nation's history to become president.

Between June 2011 and May 2012, he underwent cancer treatment in Cuba, raising speculation about his political future and a possible successor when he named 10 people to his inner circle of advisers, known as the Council of State.

But the following month he announced his re-election bid, and in July this year he declared himself cancer-free.

In a country where more than a quarter live in poverty, the charismatic Chavez has inspired "fierce loyalty" among the poor thanks largely to his social programs, according to the Center for Strategic and International Studies.

His socialist agenda has also overseen the nationalization of property and firms in numerous industries, such as finance, agribusiness, construction, oil, steel and gold.

Chavez himself came from a modest background -- born the son of schoolteachers on July 28, 1954 in Sabaneta, a city in Venezuela's Barinas state. From a young age he was influenced by Simon Bolivar, the Venezuelan soldier and politician who led the Latin American independence movement against Spain during the early 19th century. Chavez would style himself in the Bolivar mold, dubbing his own revolution "Chavismo."

His legacy will be one of both "self-styled Latin American Robin Hood" and "shrewd autocrat using and abusing his country's oil riches to stay in power," CNN's Paula Newton wrote.