Venezuela's acting President and presidential candidate Maduro raises his fist during his closing campaign rally in Caracas on April 11, 2013 REUTERS

Venezuelans will head to the polls on Sunday to choose a new leader, following former President Hugo Chavez’s death on March 5, with his protégé and acting President Nicolas Maduro commanding a strong lead in opinion polls over opposition challenger Henrique Capriles.

Massive rallies in Caracas, the Venezuelan capital, on Thursday marked the close of bitterly fought election campaigns, with Maduro tearfully vowing to complete Chavez's socialist revolution while Capriles promised change, the AFP news agency reported.

This is the second presidential election in about six months for Venezuela. More than 15 million Venezuelans who are eligible to cast ballots will choose a new successor to the late Chavez on April 14.

Marking the end of the campaign, political advertisements will be withdrawn from the news media and alcohol sales will be prohibited

Chavez, who ruled the nation for 14 years, had won re-election in October.

Capriles, the 40-year-old center-left governor of Miranda state and the candidate for the umbrella opposition group Table for Democratic Unity (MUD), won 44 percent of the vote in the October election, accounting for the strongest showing by any opposition candidate against Chavez.

Maduro, who represents the ruling United Socialist Party of Venezuela (PSUV), had been one of Chavez’s closest advisors. He is described by people close to him as a quiet and calm man who appears to have a spiritual side.

Maduro’s campaign, which relied heavily on his association with Chavez and his image as the chosen successor to carry forward the socialist revolution, played a video at every rally of Chavez giving him his blessing in an emotional last speech to Venezuelans, Reuters reported.

"I am the son of Chavez," the 50-year-old former bus driver shouted to supporters in Caracas. "I am ready to be your president."

Capriles’ campaign spent much of the time denying Maduro's claims that he would put an end to oil-funded social spending, which was one of the reasons Chavez was popular among the masses. Capriles has also promised to raise wages by 40 percent.

Reaching out to supporters of Chavez, Capriles said: "Vote for me. Nicolas [Maduro] is not Chavez.”

"I am not the opposition," Capriles said. "I am the solution."

Maduro enjoys leads of 10 to 20 percentage points in opinion polls, according to news agencies.

A survey by Datanalisis published on Thursday by Credit Suisse gave him a 9.7-point lead. The poll was conducted between April 1 and April 5.

Datanalisis President Luis Vicente Leon wrote on Twitter that Maduro's campaign was “weaker than at the beginning” but that it was not weak enough for Capriles to catch up.