Flávio Bolsonaro's first-round win lifts his runoff odds

A Bolsonaro runoff win would align nearly all of South America with the right.

In one line: Flávio Bolsonaro probably wins the 25 October runoff, but 85% overstates his edge over a candidate two points behind.

Flávio Bolsonaro topped the first round of Brazil's presidential election on 4 October with 47% of the valid votes to 45% for Luiz Inácio Lula da Silva, freepressjournal reported on 6 October. The result sets up a runoff on 25 October. wlrn_org put his share above 47% and reported that his Liberal Party won the largest bloc in the Chamber of Deputies. The New York Times called it an unexpected comeback for the Bolsonaro family.

Traders on Polymarket now give him an 85% chance of winning the presidency. That is up 26 points over the 7 days from 59% on 30 September, and up 31 points from the week's low of 54% on 2 October. The price peaked at 87% on 4 October as the count came in and has slipped 2 points since, though it gained 1.2pp in the last 24 hours. Lula's contract in the same event trades at 16%. Kalshi prices the same race at 85% for Bolsonaro and 15% for Lula, so two separate books agree.

The listed resolution date of 5 October has passed, but the rule says "This market includes any potential second round." No winner exists until the 25 October runoff, so the 85% is a forecast of that vote. Axios, via politicalwire, reported that investors did not expect Bolsonaro to top the first round so convincingly, which explains the jump. But an 85% price on a candidate who led by two points is hard to justify on the vote share alone. Lula, on 45%, must win over voters who backed other candidates, plus the abstainers he aims to mobilise, according to El País, which also reports that he will join televised debates.

The call: Bolsonaro wins on 25 October, but the 85% price overrates him, and Lula's chance sits nearer one in four than one in six. The best case for the full price is his party's place as the largest bloc in the Chamber, which suggests the shift towards the Liberal Party ran deeper than the presidential tally shows. The call is wrong if consensus reporting after the 25 October runoff names Lula the winner.

Sources