When Chávez died last month after an 18-month battle with cancer, it triggered snap elections and a brief but bitter 10-day race. The opposition has accused the ruling Unified Socialist Party of Venezuela, or PSUV, of hijacking government resources to favor Maduro.
The Capriles campaign said pro-government supporters were rallying around some voting stations and that PSUV activists were accompanying voters to the ballot box, violating their right to a secret vote.
Rosa María Camargo, a 42-year-old accountant, said she had heard reports about pro-Maduro crowds intimidating voters. As she held her 2-year-old son, she broke down in tears.
I want to have a real country for my son, not this disorder, she said. If Maduro wins, its going to be because of these abuses.
Born in Caracas in 1962 to a working-class family, Maduro was a student leftist and a bus driver before becoming a union organizer for Caracas Metro system.
His political journey ultimately led him to a jail cell where Chávez, a young military officer, was being held after trying to overthrow President Carlos Andrés Pérez in 1992. Maduro and his longtime partner, Cilia Flores, now the attorney general, worked to win Chávezs release.
Maduro helped write the 1999 constitution and became the head of the National Assembly. But he became an international figure in 2006, when Chávez plucked him from the job to become foreign minister. He held that job until October, when the ailing Chávez made him his vice president.
On Sunday, Maduro said he was going to visit the hilltop gravesite of his hero.
Commander, Maduro said. Mission accomplished.
Miami Herald Special Correspondent Andrew Rosati Contributed to this report.