RIO DE JANEIRO — In one barb epitomizing the acrimony in Brazil’s presidential race, the leftist leader Luiz Inácio Lula da Silva declared that the campaign of the centrist challenger was attacking the incumbent, Dilma Rousseff, and her supporters “like the Nazis did in World War II.”

Meanwhile, Aécio Neves, who is seeking to unseat Ms. Rousseff, compared her campaign strategist to Hitler’s propaganda minister, Joseph Goebbels. At each turn as the vote approaches on Sunday, campaigning on both sides has grown more noxious, involving personal insults, heated accusations of corruption, even a clash between campaigners on the streets of São Paulo.

The rising polarization in Brazil, which has mostly avoided the poisonous political quarrelsomeness of neighbors like Venezuela and Argentina, has stunned many voters, revealing what is arguably Brazil’s most contentious election since the end of authoritarian military rule in the 1980s.

“The entire race from start to finish has been one disgrace after another, leaving me revolted,” said Eliete Carvalho, 34, a physical therapist in São Paulo. “I never saw a race like this one. The quality of it was just horrible.”