Bolivia's interim President Jeanine Anez has said she will not run in the country's election next month, in an attempt to unify votes against the MAS party of former leader Evo Morales.

Anez, a former conservative senator, took office in the power vacuum that followed Morales's departure last year after allegations of irregularities in an October 2019 election that sparked violent protests and army pressure forced Bolivia's first Indigenous president to go into exile in Mexico. 

"Today I put aside my candidacy for the presidency of Bolivia, for the sake of democracy," Anez said on Thursday, citing "the risk that the vote is divided among several candidates and that as a result of that division, the MAS would end up winning.

"If we don't unite, Morales will return. If we don't unite, democracy loses," she said, calling for unity among voters opposed to MAS. She declined to say which candidate she planned to vote for. 

The October 18 vote is the delayed rerun of the 2019 ballot. Anez's candidacy had sparked controversy after she initially ruled herself out and pledged to guide the country to transparent new elections.

Socialist candidate Luis Arce, of the MAS party, leads in opinion polls. He is followed by centrist former President Carlos Mesa. Anez had been in fourth place.

By pulling out of the race, Anez could increase chances that the election will be pushed to a second round by consolidating the anti-Arce vote.

To avoid a second round, the election winner requires at least 40 percent of valid votes in the first round and a 10-point advantage over the closest competitor.

Arce has more than 40.3 percent support from likely voters, according to a recent poll, while Mesa stands at 26.2 percent.

Conservative anti-Morales activist Luis Fernando Camacho is projected to win 14.4 percent and Anez 10.6 percent.

Morales, who is currently living in exile in Argentina, is barred from seeking a seat in the Senate as he does not meet the residency requirements.

Morales, who was president for 13 years, denied fraud in last year's election.