Adding to those fears, some suspect their ballots won't be kept secret, despite assurances to the contrary from the Chavez-dominated National Electoral Council. The government did not invite international electoral observers, so the Capriles camp has mounted its own parallel organization of vote talliers and says it will have volunteers at every polling station feeding a central tally kept by the opposition.
Despite such concerns, voter turnout Sunday is expected to top 75 percent.
"My husband tells me he is obliged to vote for Chavez because he works with the government," said Maribel Rodriguez, a 42-year-old homemaker who lives with 83 other people in a small school in the poor neighborhood of Catia, west of the capital. "What sort of democracy do we have?"
In an April 2011 poll, the Jesuit-backed Centro Gumilla research center found that 42.6 percent of poor Venezuelans were afraid to talk politics for fear of losing government benefits or jobs. The survey of 2,000 people had an error margin of 3 percentage points.
Luis Salamanca, the political scientist who coordinated the study, said the high number, about 10 percent, of voters who won't reveal their preference or are still undecided shows many Venezuelans have "taken refuge in indecision as a protective mechanism."
Some are even stocking up on food and emergency supplies ahead of the vote.
"Here is a person who possibly won't want to concede. A person who has many years in power and for whom it would not be easy," said Belitza Perez, a 36-year-old physical therapist and the mother of a one-year-old. "Do you think that Chavez will put the (presidential) sash on Capriles? No, he is not going to give it over that easily."
On Tuesday, Defense Minister Henry Rangel added more fuel to the already charged political climate by claiming in a TV interview that Capriles plans to dismantle the country's armed forces, which is constitutionally neutral but packed with Chavez loyalists. Chavez supporters have also said some high-ranking members of the Chavez administration could face criminal investigation or lose influence overnight if their patron is voted out of office.
Marin, the Chavez-supporting security chief, couldn't be considered a high-ranking government official but he still fears what will happen to him under a new government: "I think that we would be hunted down."
Associated Press writer Vivian Sequera contributed to this report.