Ecuador's President Rafael Correa is the clear favorite to win re-election on Sunday as he has strong approval ratings and faces a fractured opposition.
Here are some details on the main opposition candidates:
Polls show the former head of Banco de Guayaquil, one of Ecuador's largest banks, is the top challenger to Correa. But the most recent survey by pollster Perfiles de Opinion, published last week, showed Lasso had just 9 percent support, 52 percentage points behind Correa.
Lasso is trying to attract middle-class voters by promising lower taxes if he wins, and incentives to private investors.
He has accused Correa of being a lackey of Venezuelan President Hugo Chavez and says leftist leaders in Latin America are implementing "franchise socialism" that suffocates the private sector with high taxes and a lack of clear investment rules.
"This ideological menu tells us the state is just about the only protagonist in development and that state-run businesses should crowd out the private businesses," he told Reuters.
Lasso, 57, may face the stigma associated with being a banker. Ecuadoreans blame banks for a 1999 financial crisis that forced the country to adopt the dollar as its currency the following year. Hundreds of thousands lost part of their savings.
A former army major who took part in a coup that overthrew Jamil Mahuad in 2000, Gutierrez was elected president in 2002 but was deposed three years later amid social unrest.
He leads the Patriotic Society Party, which has strong support in Amazon areas and a disciplined campaign team. Gutierrez, 55, is also seen as having strong support within the army and the police.
He is a populist who has offered to lower traffic fines to win support from taxi drivers.
Perfiles de Opinion shows him with 4 percent support. That may underestimate his showing on Sunday, given his strength in remote rural areas that pollsters are less likely to reach.
An economist and academic, Acosta was a close friend and political ally of Correa until the two parted ways in 2008.
He is a founder of the ruling Alianza Pais party and the former head of an assembly that rewrote Ecuador's constitution in 2008. Acosta has accused Correa of betraying the party's socialist principles and becoming more right-wing.
"He's become authoritarian, domineering, arrogant. Even if we were to assume he's done everything well, to protect the (democratic) process he needs to be replaced," Acosta told Reuters.
Acosta heads an alliance of leftist parties and grass-roots movements that is critical of Correa's drive to attract foreign investment for the oil and mining industries, which he considers a threat to the environment.
He is likely to chip away support for Correa among minority groups including indigenous people in the Amazon jungle and Andes mountains, and people of African descent in coastal areas. Perfiles de Opinion's latest poll gives him 3 percent support.
A wealthy banana magnate well-known throughout the country, Noboa is running for president for a fifth time. Polls show him winning the support of 2 percent of voters.
Noboa points out that polls showed him trailing in the 2006 election, but that he defeated Correa in the first round.
The line between Noboa's party, PRIAN, and his companies is blurred. Some of his firms' executives are also leading party members.
Noboa has campaigned on a platform of higher education spending and support for the private sector. He has come under fire for his eccentric campaign style, which has included offers to raffle off houses and company jobs to supporters, as well as handing out gifts such as food, mattresses and a motorcycle. He chose his wife, Annabella Azin, as his running mate.
Noboa is battling authorities over a multi-million dollar tax bill that the government says one of his companies owes. He says the claim is absurd and is part of a campaign of persecution intended to keep him out of politics.