Brazil Congress Will Constrain Runoff Winner
Key Facts
—Runoff Brazil votes on Sunday, 25 October 2026, from 7:00 a.m. to 4:00 p.m. ET (8:00 a.m. to 5:00 p.m. in Brasília), and results start at 4:00 p.m. ET.
—First round Senator Flávio Bolsonaro won 47.03% of valid votes (56,104,503) against 45.16% (53,879,538) for President Luiz Inácio Lula da Silva, with all polling sections counted on 4 October.
—Congress The Liberal Party (PL) holds the biggest bench in both chambers, 121 of 513 seats in the Chamber of Deputies and 28 of 81 in the Senate, so neither winner controls Congress.
—Amendments Changing the Constitution needs three-fifths of each house, 308 deputies and 49 senators.
—Prediction markets Polymarket gives Flávio Bolsonaro a 76.6% chance of winning the runoff and Lula 22.5%; Kalshi gives 79% and 21% (Monday, 19 October, 11:23 p.m. ET). Polymarket puts Flávio Bolsonaro’s chance of winning at 77% and Kalshi at 79% (Lula: 23% and 21%), as of 19 October, 11:20 pm ET; prices are bets, not polls.
—Power Index Brazil ranks 1st of 14 in The Rio Times Latin America Power Index, with 75.0 points (October 2026 edition).
Runoff · Sunday, 25 October
Brazil Runoff 2026: Lula vs Flávio
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Brazil elects its president on Sunday, 25 October, in a runoff between Senator Flávio Bolsonaro of the conservative Liberal Party and President Luiz Inácio Lula da Silva of the Workers’ Party. For US investors in Latin America’s largest economy, the vote matters as much for the Congress the winner inherits as for the name on the sash.
Bolsonaro, a son of former president Jair Bolsonaro, led the first round on 4 October with 47.03% of valid votes. Lula, who is 80, took 45.16%, and neither passed the 50% needed to win outright.
A Fragmented Congress Limits Either Winner
Press tallies of the 4 October results show the Liberal Party as the largest force in both chambers, with 121 of 513 seats in the Chamber of Deputies and 28 of 81 in the Senate. The Senate figure counts the party’s whole bench, including senators elected in earlier years.
Neither candidate would command a majority without the Centrão, the loose bloc of centre-right parties that trades votes for budget and cabinet posts. A Lula government would need that bloc to pass industrial, social and climate bills, and a Flávio Bolsonaro government would need it just as much.
Amending the Constitution requires three-fifths of each house in two rounds of voting, which is 308 deputies and 49 senators. That threshold puts big changes to tax, spending or judicial rules out of reach for a single party.
Courts and Campaign Rules Stay in Focus
The Superior Electoral Court (TSE), which runs Brazilian elections, met presidents and representatives of 24 of the 27 regional electoral courts in Brasília on 13 October to coordinate the runoff. The TSE head, Justice Kassio Nunes Marques, chaired the session.
The same day the court ordered the Liberal Party to remove an AI-generated video that linked Lula to organised crime. Simulated depictions of candidates in campaign advertising remain a live legal issue as the vote nears.
What It Means for US Readers
A Bolsonaro win would likely bring closer alignment with Washington on security, technology and critical minerals. A Lula win would more likely mean continuity on industrial, climate and multilateral policy, with both sides watching US tariffs and sanctions.
Either way, investors holding Brazilian stocks, bonds or US-listed Brazilian shares should expect a legislature that slows or waters down the winner’s plans. The real’s reaction on Monday, 26 October will show how markets read that constraint.
What Prediction Markets Say
Polymarket, with about US$189 million traded on the outcome, prices a Flávio Bolsonaro win at 76.6% and a Lula win at 22.5%. Kalshi, regulated in the US by the Commodity Futures Trading Commission (CFTC), shows 79% and 21%.
Why we show this: prediction markets turn real-money bets into a live probability that moves within minutes of the news, which is why investors, campaigns and newsrooms in the United States now follow them closely. We show them next to polls and official results, never instead of them.
Prediction markets · who wins the runoff
Implied chance of winning Brazil’s presidency on 25 October, from traders’ prices.
Polymarket
Flávio Bolsonaro 76.6% · Lula 22.5% (US$189 million traded)
Kalshi (regulated in the US by the CFTC)
Flávio Bolsonaro 79% · Lula 21%
As of 19 October, 11:20 pm ET (04:20 Lisbon), updated every 20 minutes. Prices are bets, not polls, and can move fast.
Why we show this: prediction markets turn real-money bets into a live probability that moves within minutes of the news, which is why investors, campaigns and newsrooms in the United States now follow them closely. We show them next to polls and official results, never instead of them.
What Is Not Known
Nobody knows who wins on 25 October, and polls published since the first round show a tight race that has moved from one survey to the next. Turnout and the share of blank and spoiled ballots could also change the result.
It is not yet clear which parties of the Centrão would back each candidate in Congress, or on what terms. Those talks are usually settled only after the result is known.
Sources
Superior Electoral Court (TSE) · TSE: runoff meeting with regional courts · Jornal do Comércio: final first-round count · Folha de Pernambuco · Polymarket · Kalshi
This article was produced by The Rio Times’ automated newsroom system. How we use AI · Report an error · Editorial responsibility: Matthias Camenzind, Editor-in-Chief
Frequently Asked Questions
When is Brazil’s presidential runoff?
The runoff is on Sunday, 25 October 2026. Polls are open from 8:00 a.m. to 5:00 p.m. in Brasília, which is 7:00 a.m. to 4:00 p.m. Eastern Time.
Who led the first round?
Flávio Bolsonaro of the Liberal Party led with 47.03% of valid votes, ahead of President Lula at 45.16%. Neither reached the 50% needed to win in the first round.
Why does Congress matter for the winner?
No party holds a majority, so the president must bargain with blocs such as the Centrão to pass laws. Constitutional changes need 308 deputies and 49 senators.
What do prediction markets say?
Polymarket gave Flávio Bolsonaro 76.6% and Lula 22.5% on Monday, 19 October at 11:23 p.m. ET. These prices are bets, not polls.