Nicolas Maduro holds a copy of Venezuela's Constitution as he is sworn in as Venezuela's acting president in Caracas on March 8.
Maduro, a physically imposing former union leader who served as foreign minister and vice president under Chávez, has vowed to keep Chavez's self-styled socialist revolution alive.
He will likely face off against Henrique Capriles (40) the centrist governor of Miranda state. Capriles, who lost to Chávez in a vote last October, thanked Venezuela’s opposition coalition on Saturday for backing him as its candidate, but stopped short of explicitly accepting the nomination.
Opinion polls have shown Maduro as the likely winner, but Chávez's opponents said they wanted a chance to end "Chavismo" at the voting booth.
"We want change. We are tired of the Chávez era. It's been 14 years," said Yesenia Herrera (33) a cook at a Chinese restaurant in an affluent quarter of Caracas.
Maduro was sworn in as acting president in Congress on Friday and handed the red, yellow and blue presidential sash.
"I asked [the election authority] to comply with legal and constitutional obligations and immediately call elections," Maduro (50) told Congress as he cemented his position as heir-in-waiting.
Chávez was immensely popular among the poor and they have vowed to back Maduro. Millions have filed past his casket to pay their last respects and were still visiting him on Saturday.
The Supreme Court has ruled Maduro does not need to step down in order to campaign, but the move was denounced by opponents as a violation of the Constitution and a "fraud."
As Maduro spoke in Congress, residents of some wealthy neighbourhoods of Caracas banged pots and pans in a traditional form of protest. At one building in a wealthy corner of Caracas, people drank wine and whisky around a swimming pool, rejoicing at Chávez's demise. They toasted each other, "Happy goodbye, Chávez, we will not miss you!"
Hero or autocrat?
Chávez was a hero to millions of mostly poor supporters for using Venezuala’s oil wealth to finance heavy social spending, but he was seen as an autocrat by his opponents. He died on Tuesday at age 58 after a two-year battle with cancer.
"The excluded and invisible, the 'losers' of savage capitalism, were made visible and victorious with Chávez," Information Minister Ernesto Villegas said on Twitter.
José Vielma Mora, the governor of Tachira state, called Chávez a "liberator".
"He liberated us from transnational companies and stood up to imperialist countries," he said. "We will be with Chávez forever."
Like communist leaders Lenin, Stalin and Mao, Chávez 's remains are to be embalmed and put on display "for eternity".
An eclectic cast of celebrities, leftist and centre-right presidents attended Chávez's state funeral on Friday. Iranian President Mahmoud Ahmadinejad, a close ally, broke with protocol to kiss the coffin, while Oscar-winning actor Sean Penn was also in attendance.
It is likely to be a particularly bitter election campaign in the Opec heavyweight nation, which boasts the world's largest proven oil reserves.
The opposition had accused the government of trampling on the Constitution during its handling of Chávez’s battle with cancer, and is furious Maduro was allowed to take on the job of caretaker president while he campaigns for the job.
"This transgression is unprecedented in the history of the republic," opposition lawmaker Maria Corina Machado said on Twitter.
Capriles called it an abuse of power.
"To become president, the people have to elect you," he said on Friday. "No one elected Nicolas president." – Reuters