Dominican Republic elections: Key issues
With more than 4,300 seats up for election, local media have called 15 May "the most complex" election day in the history of the Dominican Republic.
Dominicans will elect a president, a vice-president, members of both chambers of Congress and municipal councillors - all on the same day.
The last time such a large number of posts was up for election was in 1994.
The elections feature the country's first female presidential candidates and the possibility of President Danilo Medina's re-election.
There are also questions over the vote-counting system.
Because of a constitutional change approved in June 2015, President Danilo Medina has been allowed to seek a second consecutive term.
Mr Medina is presently the front-runner among the eight candidates standing for president with more than 65% of voters saying they intend to vote for him, according to a recent poll by Gallup-Hoy.
The same poll also indicated that 70% believed Mr Medina had greater leadership capabilities than the other candidates.
The polls suggest Mr Medina could become the first candidate to get the 50% of the votes needed to win outright in the first round, eliminating the need for a second round.
The two-round system was introduced by constitutional reform in 1994.
Relations with Haiti
Although Mr Medina currently enjoys a high level of popularity in the country, his foreign policies with regard to neighbouring Haiti have been widely criticised by his rivals.
Tense relations with Haiti have been a key topic in the campaign.
Large numbers of Haitians have migrated - many of them illegally - to the Dominican Republic, to escape the poverty and lack of employment in their homeland in recent decades.
The presidential candidate for the National Progressive Force (FNP) and the Sovereign Front, Pelegrin Castillo, has proposed building a wall at the border.
He says he wants to send a message to the world that the Dominican Republic cannot be the solution to Haiti's problems.
In contrast, Mr Medina's main rival, opposition leader Luis Abinader, said he would be interested in a free-trade agreement with Haiti, as well as the implementation of an immigration law.
He also wants to strengthen the country's border security agency, Cesfront,
First female presidential candidates
Out of the 56 candidates who have run for the Dominican presidency since 1962, all have been men.
But in Sunday's election, two women will be running for the top job: Soraya Aquino and Minou Tavarez Mirabal.
The two have diametrically opposed views on some key issues.
Conservative candidate Ms Aquino has vociferously opposed to same-sex marriage.
"While I am still able to breathe and while I have a voice, that [same-sex marriage] will not be accepted. We have these people, but we will block their inclusion," she said.
In contrast, Ms Tavarez has spoken out in favour of LGBT rights. She also backs the legalisation of marijuana and is pro-choice on abortion.
Many Christian groups in the country have campaigned against her because of her positions on these issues.
Concerns about the count
Given the large number of seats being contested, there have been concerns about the vote count.
Presidential candidate Guillermo Moreno, who is standing for the Country Alliance (Alianza Pais) and the Modern Revolutionary Party (PRM), has asked the Central Electoral Board to count the votes by hand.
He said he had doubts about the electronic voting system, which will not be audited by the regional body, the Organization of American States, because of a lack of funds.