Three weeks ago, Luiz Inácio Lula da Silva finished second. On Sunday night, October 25, he won Brazil's presidency for a fourth time with 51.79 percent of the vote to Flávio Bolsonaro's 48.21, a margin of 4,430,191 votes according to the Superior Electoral Court (TSE). France 24 reported it is the first time since Brazil's return to democracy that a candidate who lost the first round came back to win the runoff. Then the dispute began.

The result

Lula received about 64.26 million votes to 59.83 million for the 45-year-old senator, according to the electoral court's count, with all polling sections reported. In the first round on October 4, Lula had taken 45.16 percent and Flávio 47.03. That is a gain of 6.6 points for the president and 1.2 for his challenger.

Reuters said Lula's win defied polls, precedent and a global anti-incumbent mood, and slowed a wave of right-wing victories across Latin America. It will also disappoint the Trump administration, whose State Department led a campaign to return the Bolsonaros to power, Reuters reported. The president, who is 80, will govern from 2027 to 2030 facing a Congress where Bolsonaro's Liberal Party holds its largest bench in decades, and with public debt he will need to stabilize, CNBC noted.

Where the swing came from

Before the runoff, simple arithmetic suggested Lula would need about 62 percent of the voters who backed other candidates in round one to close a two-point gap, assuming the same turnout. Turnout did not stay the same. PBS reported that millions of Brazilians who did not vote in the first round came out on Sunday, with voters in Rio de Janeiro and the suburbs of São Paulo swinging to Lula.

Geography tells the rest. In Minas Gerais, the state with Brazil's second-largest electorate, Lula went from losing by nearly 590,000 votes to winning by about 99,000, a swing of roughly 690,000, CNN reported. Flávio kept his lead in the states of São Paulo and Rio de Janeiro, but Lula won both capital cities and reversed the first-round result in the city of Rio.

The polls have now missed twice in three weeks. Our preview before the first round reflected surveys that had Lula ahead, and Flávio won that round. In the runoff, surveys pointing to a Flávio win underestimated Lula, as Reuters noted when it said the result defied the polls. It is a warning against reading any single survey as a forecast.

The dispute

The result is not being accepted by the loser. Flávio Bolsonaro followed his imprisoned father's lead and refused to concede, saying he would seek the annulment of the election, Reuters reported. His objection centers on a late-Sunday decision by a Lula-appointed Supreme Court justice that extended voting by two hours over alleged irregularities in voter transport. Another outlet identified the justice as Cristiano Zanin.

Reuters noted that the refusal could spark protests in a country where trust in the electoral system and judicial independence has been strained. Analysts do not give the legal challenge much chance. UBS's Justin Wensek told clients the annulment request was unlikely to hold up because of the 4.4 million-vote gap, according to HNGN's report.

The arithmetic points the same way. To overturn the result a challenge would need to show that problems tied to a two-hour extension affected more votes than the margin. The coverage available does not say how many voters used the extra time.

Trump's reaction

US President Donald Trump said on Monday that the vote "looked like another rigged election," without providing evidence, Reuters reported. He added that he had not taken sides. Donald Trump Jr. had criticized the Supreme Court's decision to extend voting hours, according to Time. Leaders from across Latin America largely congratulated Lula, CNBC reported, while Trump was among the notable exceptions. Reuters described the Trump administration as having led a campaign to return the Bolsonaros to power.

The line between a candidate's right to challenge and a refusal to accept a clear result is the issue observers are watching. Brazilian courts are open to legal challenges. A claim of rigging without evidence is something else, and it has precedent in Brazil: Jair Bolsonaro also did not concede in 2022.

The market verdict

Brazilian assets sold off sharply. The real fell about 11 percent against the dollar and trading in São Paulo was halted for 30 minutes after the open, according to a report by HNGN, and a Tokyo-listed fund that tracks the Bovespa index dived nearly 15 percent in Asian trading, Reuters said. CNBC described it as unwinding some of the rally that followed Flávio's first-round lead.

Investors had rallied after Flávio's first-round lead on the prospect of a change of direction, and Lula's win reversed part of that. He now faces a large public debt to stabilize and a Congress where the opposition holds the largest bench.

What it means

PBS described Lula's win as decisive but far from a mandate. A 3.6-point margin, a hostile legislature and a loser who will not concede make for a difficult start. The next test is institutional. The electoral court will certify the result, the annulment request will be heard, and Flávio Bolsonaro's supporters will show whether they treat it as a legal matter or as a call to the street.

For Lula the political arithmetic has not changed. He won by getting people who stayed home in round one to vote. Keeping them engaged will matter more than anything he does in the first week.

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