Traders tilt towards a narrow Flávio Bolsonaro win

The four-to-eight-point band falls 21 points in a week as a sub-four-point win becomes favourite.

In one line: Flávio Bolsonaro wins Brazil's 25 October runoff by four to eight points, a result traders now underrate at 33%.

Traders have cut the chance that Flávio Bolsonaro wins Brazil's second round by four to eight points from 54% on 8 October to 33% on 15 October, a fall of 21 points over the seven days. The contract lost 12.0pp in the last 24 hours (the venue's own figure), and it sits 2 points above the seven-day low of 31% it touched on 14 October. The vote is on 25 October and the contract resolves on 26 October.

The other brackets in the event show where the money went. A Flávio win by less than four points now trades at 40%, the most expensive band. A win by eight to twelve points sits at 12% and one by twelve or more at 3%. Polymarket and Kalshi price a Flávio victory at 83% and 84% respectively.

The read here is that the margin brackets and the win price pull against each other. Two independent books make Flávio a clear favourite, yet the margin market now treats a win by under four points as its single most probable result. The week's slide in the four-to-eight band may reflect traders marking the race tighter, while both venues still price a Flávio victory at 83% and 84%.

A Flávio win by four to eight points is more likely than the 33% price allows. The price path is the main argument against this call: a week of steady selling has made the sub-four band favourite, and if that money is tracking a tightening race, the 40% contract is the better guide. The official count of valid votes after the 25 October vote settles it, and a margin under four points or over eight, or a Flávio defeat, proves this call wrong.