President Luiz Inácio Lula da Silva and groups monitoring social media say search results omit progressive activists, videos critical of the right-wing challenger are taken down without explanation and posts lauding Lula reach fewer people.

Lula’s campaign, which is racing to shore up millions more votes ahead of a runoff against Bolsonaro on Oct. 25, filed a complaint with the nation’s electoral court on Saturday, demanding fair treatment online.