Former Venezuela presidential candidate and high-profile figure Henrique Capriles broke opposition ranks on Thursday and called for a high turnout in December's elections.
Opposition leader Juan Guaido has led a group of 30 opposition parties calling for a boycott of the election due to a lack of transparency and fears President Nicolas Maduro won't allow it to be free or fair.
But Capriles, a presidential candidate in 2012 and 2013, said he would not leave Venezuelan voters "without options."
"I call on the country to mobilize and fight ... we're not going to gift the National Assembly to Maduro," said Capriles on his social media channels.
The National Assembly is the only government branch in opposition hands and Maduro is determined to regain control of it in December.
But Guaido called for a boycott after the Supreme Court, which is loyal to Maduro, appointed the officials to run the electoral body overseeing the poll.
That's a job that should be done by the National Assembly.
The Supreme Court has previously shown itself to be loyal to Maduro, trying to bar some opposition lawmakers from being sworn in once Maduro's socialist party lost control of the legislature in 2015.
After the assembly swore them in anyway, the Supreme Court ruled it was in contempt and has annulled every decision it has taken since.
But rather than boycott elections that have been dismissed by top European Union diplomat Josep Borrell as lacking "the conditions for a transparent, inclusive, free and fair electoral process," Capriles wants to "open the way" and "fight for the conditions" to stage a credible poll.
"We're not going to leave the people without options," said Capriles, who hit out at Guaido over his failure to dislodge Maduro in more than a year and a half since making the bold move to declare himself acting president.
While Guaido won backing from more than 50 countries, Maduro retains the support of the powerful armed forces and has not budged.
"What's the plan?" said Capriles. "To play at being president over the internet? We have to save Venezuela, comrades, save it!"
Capriles, who founded First Justice -- one of the main opposition parties -- and his deputy Stalin Gonzalez have been accused of holding talks with Maduro's government before backing the election.
Capriles, who has been barred by the regime from holding public office since 2017, said he was prepared to speak to whomever could help bring about a "credible solution" to Venezuela's political crisis.
Earlier this week, Maduro pardoned more than 100 opposition lawmakers and associates of Guaido, while also inviting the United Nations and EU to act as observers for the elections.
Guaido dimissed both moves as a ploy to try to legitimize the elections.