The country's National Electoral Council says that more than 1,500 polling stations are open nationwide for the mock vote.
In the streets of Caracas, supporters of President Hugo Chavez and challenger Henrique Capriles say the drill has been going smoothly.
But opposition politician Leopoldo Lopez is accusing Chavez's team of using state funds to mobilize people to the polling stations. Lopez is calling on the electoral council to investigate.
The drill had originally been scheduled a week earlier but was delayed due to last weekend's deadly blast at the country's biggest refinery.
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