The 59-year-old leftist who has been in office for nearly 14 years was favored to win the first round vote. But polls suggested South America's longest-serving leader would likely be forced into a December runoff in which he could be vulnerable to a united opposition.
Voting, which was mandatory, was mostly calm, though police said they arrested more than 100 people for violating the country's rigid election-day rules against drinking, large gatherings or casual driving.
Morales voted early and said he remained confident of the results. Polls closed at 4 p.m. and early quick counts were expected Sunday night. Morales came to prominence leading social protests and won election as Bolivia's first indigenous president in 2006.
The president, a former leader of a coca growers union, 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%, well above the regional average.
Morales, the son of Aymara Indian shepherds, has also been credited for battling racial inequalities. Many Bolivians, such as vendor Celestino Aguirre still identify with "Evo," as he's widely known, saying people shouldn't criticize him so much. "It's not against Evo, it's against me, against the poor people, against the humble."
But Morales also has faced growing dissatisfaction even among his indigenous supporters. Some are frustrated by corruption scandals linked to his administration — though not Morales himself — and many by his refusal to accept a referendum on limiting presidential terms. While Bolivians voted to maintain term limits in 2016, the country's top court, which is seen by critics as friendly to the president, ruled that limits would violate Morales' political rights as a citizen.
"I'm thinking of a real change because I think that Evo Morales has done what he had to do and should leave by the front door," said Nicolás Choque, a car washer. Mauricio Parra, who administers a building in downtown La Paz, said he voted for Morales in 2006 as a reaction against previous center-right governments.
"He did very well those four years. ... (But) in his second term there were problems of corruption, drug trafficking, nepotism and other strange things," Parra said, saying that led him to vote against repealing term limits in the 2016 referendum. "He hasn't respected that. That is the principle reason that I'm not going to vote for Evo Morales."
Parra said he was backing Morales' closest rival, former President Carlos Mesa, a 66-year-old journalist and historian who as vice president rose to the nation's top post when his predecessor resigned in 2003 amid widespread protests. He then stepped aside himself in 2005 amid renewed demonstrations led by Morales, who was then leader of the coca growers union.
An Oct. 4-6 poll by San Andres Higher University and other institutions said Morales led Mesa 32% to 27% heading into the first round of voting, with the rest split among other candidates. But to win outright, Morales needed to get 50% plus one vote or finish with 40% of the votes and be 10 percentage points ahead of the nearest challenger. Without that happening, the top two finishers would go to a runoff, and the poll indicated Morales and Mesa were practically tied at just under 36% each in a two-way race.
The rest of those surveyed said they were undecided, would cast a null ballot or declined to state a preference. The poll surveyed 14,420 people and the margin of error was three percentage points. Bolivians were also electing all 166 congressional seats. Polls projected that no party would have a majority in Congress, which could lead to an impasse for the upcoming administration.