Ecuadorians are voting in the first round of elections to choose a new president.
Left-wing incumbent Rafael Correa is standing down after leading the country for a decade.
His former vice-president Lenin Moreno is expected to lead Sunday's vote, but is facing a strong challenge from conservative Guillermo Lasso, who has vowed to cut spending and taxes.
Candidates need to win 40% of the vote to avoid a second round run-off.
- Who will succeed Rafael Correa?
Mr Correa, who was elected in 2007 and is unable to stand again, oversaw an economic boom during his 10 years in power.
But a slump in the price of oil meant the oil-exporting country was unable to continue supporting its poverty reduction programmes, and was criticised for not putting money aside for hard times.
Recent corruptions scandals have also cast the ruling party in a more negative light, and some have speculated that Ecuador will follow Peru and Argentina in electing a conservative government.Image copyright EPA Image caption Candidates need 40% of the vote to avoid a second round run-off
Centre-right Mr Lasso, a former banker, wants to create a million jobs.
Among his other election pledges is one to withdraw asylum rights from Wikileaks founder Julian Assange, who has been holed up in the Ecuadorian embassy in London since June 2012.
However, Mr Moreno, a key figure in Mr Correa's cabinet between 2007 and 2013, is predicted to win Sunday's vote, but not with enough to avoid the second round run-off.
Mr Moreno, who became paraplegic after being shot in the back in 1998, has most recently served as UN Special Envoy on Disability and Accessibility.
Voting is mandatory in Ecuador, and 12 million people are expected to cast their ballot on Sunday, starting at 07:00 local time (12:00 GMT), with polls closing at 17:00 local time (22:00 GMT).
Results are expected from about 20:00 (01:00 Monday, GMT).