LA PAZ, Bolivia — When he was 46, Rene Paucara voted for Evo Morales, helping elect him as Bolivia’s first indigenous president in 2005.

At 56, Mr. Paucara, a doorman in El Alto, Bolivia’s second-largest city, voted with the majority again, but that time to reject a 2016 referendum to let Mr. Morales seek a fourth term.

Now nearing 60, Mr. Paucara says he is fuming: Mr. Morales has said he will run again anyway. The president has been aided in the courts, which threw out the country’s term limits, describing them as unfair to politicians like Mr. Morales, a leftist who has reshaped Bolivia in his dozen years in power.

Mr. Paucara now fears that if the president wins again next year, he may be well on track to keep the job for life, unwilling to hand over his office to any successor.