Brazil’s presidential election will be decided in a runoff on October 25. Here is what happened and what comes next.

In the first round on October 4, Senator Flavio Bolsonaro led with 47.2 percent of the vote. President Luiz Inacio Lula da Silva got 44.9 percent. Because no candidate won more than 50 percent of valid votes, the top two advance to a second round.

The result shocked pollsters. Most surveys had given Lula, 80, a single-digit lead. On the eve of the vote, Datafolha put Bolsonaro at 42 percent against 45 percent for Lula.

Flavio Bolsonaro, 45, is the eldest son of imprisoned former president Jair Bolsonaro. He dominated the south, winning Sao Paulo 52 to 38, Minas Gerais 50 to 43 and Rio de Janeiro 53 to 39.

Conservatives also swept concurrent congressional and state races. The campaign was one of the most vicious in Brazil’s democratic history, with neither candidate attending the televised debates.

The runoff is now the biggest test yet of Latin America’s conservative shift. Polls had shown the two statistically tied in a runoff scenario, but after Sunday’s miss, every survey will be treated with caution.