Acting President Nicolas Maduro holds a comfortable lead in most pre-election polls, although late polls have challenger Miranda state Governor Henrique Capriles closing the gap slightly.
But as we all know, polling in an oppressed society is an iffy proposition. People responding to questions don't really know if they declare for the challenger if that information won't get back to the authorities. So any poll taken in Venezuela should be viewed as suspect.
Nevertheless, Maduro has enormous advantages, including a state media monopoly, and cadres of Chavista thugs who may "monitor" the election to make sure people vote "properly."
Will there be a surprise surge by Capriles? And if there is, will the state electoral machinery shift into high gear and steal the contest for Maduro?
Maduro, a 50-year-old former bus driver who has trumpeted his working-class roots at every rally, is promising to push forward Chavez's "21st century socialism" if he triumphs.
"We're going to have a giant victory. The bigger the margin, the more peaceful the country will be," the brawny, mustachioed Maduro said. "If the gap is smaller, it is only because they (the opposition) managed to confuse a group of Venezuelans."
The winner will inherit control of the world's biggest oil reserves in an OPEC nation whose stark political polarization is one of Chavez's many legacies.
Also at stake is the generous economic aid Chavez provided to left-leaning Latin American governments from Cuba to Bolivia.
From the country's Caribbean coastline to its cities and jungle interior, polling centers were due to open from 6 a.m. (0630 EST) until 6 p.m. (1830 EST), though voting could run longer if there are still lines.
Both camps have urged supporters to vote early and be on alert for fraud. Given the deep mutual mistrust, a close or contested result could raise the chance of unrest.
Chavez's fourth presidential election win in October saw record turnout of 80 percent. This time, though, both sides worry that participation could be lower because of election fatigue.
Many Venezuelans could be forgiven for feeling like they are stuck in a never-ending campaign. Opposition primaries early last year were followed by the ailing president's dramatic re-election, and then a vote to choose state governors in December.
Maduro has cloaked himself in the imagery of Chavez and calls himself the late president's "son." At events around the nation, supporters chanted "With Chavez and Maduro, the people are safe!" and "Chavez, I swear to you, I'll vote for Maduro!"
At every rally, Maduro played a video of Chavez naming him as successor in December - "my firm opinion, clear like the full moon, irreversible" - in his final speech to Venezuelans.
The Chavistas are far better organized than the opposition so a low turnout will probably favor Maduro. But the acting president does not have Chavez's charisma or ability to move his supporters. If Capriles can motivate the Middle Class to vote in huge numbers, his chances will increase substantially.