Flávio Bolsonaro beat outgoing President Lula in the first round of the Brazilian presidential election, with 47.03% of the vote against 45.16%, sending the outcome to a second round on October 25. The polls showed Lula winning; the prediction platforms had been seeing the senator’s lead since September. A denial which reignites the debate on their reliability, while they are blocked in Brazil.
In brief
- Flávio Bolsonaro (47.03%) beat Lula (45.16%) in the first round; the second round will take place on October 25.
- On Polymarket, the senator’s rating increased from around 22% in July to more than 80% after the election.
- Betting on ballots has been banned in Brazil since a regulation came into force in May.
A first round against the polls
Already under fire in the United Kingdom, predictive markets closely followed the campaign in Brazil. On Sunday, however, the results showed a discrepancy with the main opinion polls.
Flávio Bolsonaro, senator and son of former president Jair Bolsonaro, received 47.03% of the vote, compared to 45.16% for Lula. Neither candidate having obtained an absolute majority, the second round will take place on October 25.
However, Datafolha placed Lula in the lead with 42% of voting intentions, compared to 38% for Flávio Bolsonaro. Other polls also predicted a very close vote.
After the announcement of the results, Lula admitted having thought he could win in the first round and called on his supporters to continue the campaign.
I was sure of winning the election in the first round. Bolsonaro represents uncertainty for the country.
The odds had changed in September
On Polymarket, the contract dedicated to the Brazilian election, launched in September 2025, exceeded $171 million in cumulative trade.
At the beginning of July, Flávio Bolsonaro had around a 22% chance according to the platform’s odds, compared to 60% for Lula. Then, from September, the trend reversed. On September 20, the senator reached around 58%, while Lula fell to 42%. Kalshi showed a comparable development.
After the first round, Flávio Bolsonaro’s rating climbed to around 82%, compared to 17.5% for Lula, according to data recorded on Monday.
The 2024 American election had already drawn attention to this gap between polls and predictive markets. For the mid-term elections, the two approaches converge this time towards a Democratic scenario.
Markets without Brazilian voters
This comparison, however, deserves an important nuance. There National Monetary Board Resolution 5.298which came into force on May 4, prohibits derivatives linked to political, electoral, sporting or cultural events.
The Ministry of Finance then ordered the blocking of 27 platforms, including Polymarket. In July, the latter limited Brazilian accounts to closing their positions. In other words, the participants who influenced these markets were not representative of Brazilian voters.
The phenomenon also goes beyond Brazil. In France, Polymarket was blocked before a 2027 presidential election which was already very popular on the platform. Elon Musk’s reactions to X in late September also helped bring attention to these markets.
The second round on October 25 will therefore shed new light on the gap between polls and predictive markets. But their particular audience remains an essential element to take into account when analyzing their results. Their role continues to spark debate.
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