Voters in two island nations off Africa's western coast went to the polls Sunday to pick new presidents.

In Sao Tome and Principe, voters cast ballots in a second-round run-off between former President Manuel Pinto da Costa and Parliament Speaker Evaristo de Carvalho.

Da Costa, who led a one-party socialist state from 1975 to 1990, is the favorite to win. The former president won the first-round voting with 35 percent and has earned the backing of most of the eliminated candidates.

The winner will succeed President Fradrique de Menezes, who is constitutionally barred from seeking a third term.

In the West African archipelago of Cape Verde, voters picked between four candidates to replace President Pedro Pires, who has also served the maximum two terms.

The ruling African Party has nominated Manuel Inocencio Sousa as his successor. Sousa is being challenged by a former party member, Aristides Lima, opposition leader Jorge Carlos Fonesca, and independent Joaquim Monteiro.

Both Sao Tome and Cape Verde are former Portuguese colonies that won independence in July 1975.

Since then, Sao Tome has suffered chronic poverty and periodic instability highlighted by failed coup attempts in 1995 and 2003. The two-island nation, located in the Gulf of Guinea, is believed to have significant oil reserves and the potential for a tourism industry.

In contrast, Cape Verde, located in the Atlantic Ocean off Mauritania, has enjoyed stability and steady economic growth despite chronic drought. Tourism, transport, and remittances from emigrants form the backbone of the economy.