SAN JOSE: Costa Ricans could elect their first female president Sunday as Central America's most politically and economically stable country chooses between a career politician from the ruling party and an anti-taxation Libertarian.

Pre-election polls gave a nearly 20-point lead to Laura Chinchilla, who served as vice president under current President Oscar Arias, a Nobel Peace Prize winner and free market enthusiast.

Otto Guevara, of the Libertarian Movement Party, emerged as Chinchilla's biggest challenger. He promised to lower taxes, dismantle monopolies and adopt the U.S. dollar as the country's currency.

Otton Solis, who barely lost the presidential election to Arias in 2006, came in third in the opinion polls.

Sunday's winner needs at least 40 percent of the vote to avoid an April run-off.

If victorious, Chinchilla has pledged to continue Aria's moderate free-market policies that brought Costa Rica into the Central American Free Trade Agreement with the United States and initiated trade relations with China after a 63-year association with Taiwan.

But critics of the government say Arias catered to big developers to boost the economy at the cost of the nation's fragile ecosystems.

Both Solis and Guevara portrayed Arias' centrist National Liberation Party as stagnate and ridden with old-school Latin American crony politics.

It was unclear whether the National Liberation Party had the strength to win a legislative majority in Sunday's voting.

But most Costa Ricans appeared reluctant to shake up the status quo in a country with relatively high salaries, the longest life-expectancy in Latin America, a thriving eco-tourism industry and near-universal literacy.

Chinchilla, as a 50-year-old mother and a social conservative who opposes abortion and gay marriage, appealed both to Costa Ricans seeking a fresh face in politics and those reluctant to risk the unknown.

If Chinchilla wins, she would become Latin American's fifth female president. Nicaragua, Panama, Chile and Argentina have all elected women as presidents.