Anez, a 52-year-old conservative who took office amid a power vacuum following Morales' resignation under pressure last year, said she was calling this week for a summit of political parties to help defeat Morales' Movement to Socialism (MAS).
She said, however, that she currently has no plans to run herself. Morales himself is in Argentina and has said he will not take part in May's election, but he is playing a key role in the campaign of the party he founded.
"If we dilute the vote obviously that will benefit Evo Morales," Anez said in an interview with Reuters at the presidential palace in the historic center of La Paz. "We can not risk a return to the same 14 years of oppression and authoritarianism of Evo Morales, who is totally sick for power."
The scrabble to unite the opposition underscores the challenge for Bolivia's conservatives in an election that could be key in deciding the future direction of the gas and lithium rich nation.
Anez, president almost by chance after she took over according to a line of succession when Morales and his deputy resigned, is at the heart of a political storm that has rocked Bolivia, where the image of Morales was ubiquitous from public transport to sports stadia for more than a decade.
Morales stepped down on Nov. 10 after a disputed election victory a month earlier sparked protests and led to allies, police and military pulling their support.