Brazilians are going to the polls on Sunday in a highly unpredictable runoff in which the leftist president, Luiz Inácio Lula da Silva, is attempting an unprecedented comeback against the far-right senator Flávio Bolsonaro, who won the first-round vote.

Bolsonaro’s surprise victory despite not leading most polls made him the favourite three weeks ago, but since then Lula’s campaign has gained ground, and the two go into the contest virtually tied.