Sen. Flávio Bolsonaro is gathering allies fast for Brazil's presidential runoff. On Tuesday, two centrist parties, the Progressives (PP) and Brazil Union, said they would back him against President Luiz Inácio Lula da Silva on Oct. 25, O Globo reported.

The two parties form an alliance and stayed neutral in the first round. Both have people serving in Lula's government. PP's Senate leader, Tereza Cristina, said the vote to back Bolsonaro was unanimous. O Globo called the move a setback for Lula, though his camp had expected it.

Other names joined too. Ronaldo Caiado, who placed fifth, endorsed Bolsonaro at an event in Goiás on Tuesday. Former Minas Gerais Gov. Romeu Zema had already backed him. Former President Michel Temer also endorsed him. "Reconnection is Flávio," Temer said, according to Valor International.

Not everyone is moving. Caiado's own party, the PSD, said it would stay neutral. Bolsonaro also met the leader of the Republicans party. Valor reported that party may stay neutral because the speaker of the lower house, a member, backs Lula. O Globo said the party leans toward Bolsonaro but will not punish members who back Lula.

Lula's allies hope to win over some leaders of these parties, including the Senate president, Davi Alcolumbre. They are also pushing a constitutional change in the Senate to end Brazil's six-day workweek, which they hope will help Lula.

Bolsonaro skipped TV debates in the first round, and so did Lula. On Tuesday, he said he will debate. "I want to compare the programs of government," he said, according to Estadão. Band and Estadão set the first runoff debate for Oct. 18 at 8 p.m. Brasília time, a week before the vote. It will air on Band and stream on Estadão's site and YouTube.

In Sunday's first round, Bolsonaro won 47.03% of valid votes, about 56.1 million. Lula won 45.16%, about 53.9 million.

Some background: Flávio is the eldest son of former President Jair Bolsonaro, who was barred from running. Lula is seeking a fourth term. O Globo noted Flávio is under a Supreme Court inquiry over asking a banker for money to fund a film about his father.

What we know: Bolsonaro has new party backing and a debate date.
What we don't: How runoff polls will look once fresh surveys are released.