LA PAZ, Bolivia (AP) — South America's longest-serving leader is seeking an unprecedented fourth term in Bolivian elections on Sunday, but polls suggest Evo Morales is in the tightest race of his career.

The 59-year-old leftist is favored to win the first round vote, but he's likely to be forced into a December runoff where he could be vulnerable to a united opposition.

The son of impoverished Aymara shepherds, Morales came to prominence leading protests and won election as Bolivia's first indigenous president in 2006.

He allied himself with a leftist bloc of Latin American leaders and used revenues from the Andean country's natural gas and minerals to redistribute wealth among the masses and lift millions out of poverty in the region's poorest country. The economy has grown by an annual average of about 4.5%.