Dominican leader wins third term
Miguel Vargas Maldonado conceded after early results confirmed exit poll predictions giving the president a clear lead in his bid for a third term.
With 30% of votes counted, President Fernandez has 53% support.
"I accept and recognize the results of the elections," said Mr Vargas Maldonado, the social democrat leader, at his campaign headquarters.
But he refused to congratulate Mr Fernandez, saying the election had been marred by "the most shameful use of state resources."
The Central Electoral Commission released results showing Mr Fernandez had obtained 576,000 votes out of the 1 million counted so far.
If he can obtain 50% of the votes overall, the president will win outright without the need for a second round of run-off voting.
The head of his campaign, Francisco Javier Garcia, said that a count carried out by Mr Fernandez's centrist Dominican Liberation Party showed that he had won 54% overall.
"We got the result in the first round," said Mr Garcia.
No figures have so far been given for the turn-out among the 5.7 million registered voters.
Correspondents say Mr Fernandez is widely credited with having revived the Dominican Republic's economy during his four years in office, but has promised to do more to fight poverty if re-elected.