Official results in Bolivia with four of five ballots counted show 54 percent of voters rejecting President Evo Morales' bid to change the constitution so he can run for a fourth consecutive term in 2019.
Bolivia's vice president is claiming a right-wing conspiracy to steal the election in the countryside. Support for Morales is stronger there and ballot-counting slower.
Vice President Alvaro Garcia Linera didn't provide evidence to back his allegations.
Ballot-counting has been unusually slow from Sunday's referendum, though international observers say there is no evidence of fraud.
Government transparency in the vote count has been questioned, with the results page on the electoral tribunal's website often inaccessible.
Repeated attempts by The Associated Press to reach tribunal officials by phone Tuesday were unsuccessful.