Costa Ricans are voting Sunday for a new president and congress after a campaign in which gay marriage displaced soaring debt levels as the main topic of contention.
One candidate is Fabricio Alvarado, a conservative Christian singer and TV personality.
But as the only major candidate openly backing same-sex marriage, Carlos Alvarado also saw his poll numbers rise about 5 percent recently as he attracted socially liberal voters who oppose Fabricio Alvarado's anti-gay marriage stance.
If no candidate receives at least 40% of the 4 February vote, a runoff election with the top two candidates will happen in early April.
Rival Antonio Alvarez, a banana entrepreneur and candidate of the National Liberation Party, has said while he personally opposes the court's decision, he would respect it if he wins.
The court's panel of 15 worldwide judges also found that Costa Rica has sovereignty over the "whole northern part of Isla Portillos, including the coast", but excluding Harbour Head Lagoon.
Carlos Alvarado, who is not related to Fabricio, is also a young candidate at just 38, a journalist by profession who began his political career as communications director for the Citizens' Action Party and served as labor minister under current President Luis Guillermo Solis.More news: Mondelez International Inc (NASDAQ:MDLZ) Stake Increased by Koshinski Asset Management Inc
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The outlook was cloudy because none of 13 candidates was polling at more than 17 percent, and surveys indicated that more than a third of likely voters were undecided.
Elsewhere in the region, gay and lesbian couples can marry in Argentina, Brazil, Colombia, Uruguay and in parts of Mexico.
The United Nations' highest judicial body ruled today on two of Costa Rica's cases, finding that Nicaragua should pay for the removal of close to 300 trees and 6.19 hectares of vegetation.
"The main issue to be dealt with is the fiscal deficit", said Vidal Villalobos, head of economic studies for Prival Bank S.A. "Markets are very aware of Costa Rica's fiscal problems and the country is paying for it".
Solis, a former diplomat and history professor, won in a landslide four years ago but has seen his popularity slide as an investigation into an influence peddling scandal has unfolded.
Solis gained worldwide attention when he hoisted a rainbow flag along with the Costa Rican flag atop his office just a week after he took office as a statement against homophobia.
Costa Rica's 3.3 million residents are predominantly Roman Catholic and most consider themselves conservative.