Turnout at voting centers appeared light in Managua on Sunday.
His government has arrested at least three dozen leading opposition figures, including seven potential presidential candidates, on what are widely viewed as spurious charges.
The opposition had called on Nicaraguans to stay home in protest of an electoral process that has been roundly criticized as not credible by foreign powers.
Voting was orderly and speedy as voters noted the absence of long lines at more than 13,000 polling places around the country.
Nicaragua is set to hold elections on Nov.