Polymarket's contract on a Flávio Bolsonaro win recovered to 87.05 cents, closing most of Monday morning's gap with Kalshi. BTG/Nexus, Quaest, Datafolha and Palver all publish between Tuesday and Thursday.
The price difference between the two biggest event markets on Brazil's presidential runoff has mostly closed, a day before four national polls publish in three days.
Polymarket's contract on Sen. Flávio Bolsonaro winning the Oct. 25 runoff against President Luiz Inácio Lula da Silva rose from 86.3 cents early Monday to 87.05 cents by early afternoon. On Kalshi, the equivalent contract traded between 87 and 88 cents all day and last changed hands at 87 cents at 1:14 p.m. Eastern. The gap, about 1.7 cents early Monday, is now within a cent.
The trading
Kalshi's session was two-sided. The largest trades included about 2,700 contracts sold at 87 cents at 9:11 a.m., trades totaling about 5,400 contracts bought at 88 cents at 11:26 a.m. and 1,500 bought at 88 cents at 12:39 p.m. The price did not trend in either direction.
Polymarket's recovery came mostly in the early morning, with a final uptick around 1 p.m., and with no identified catalyst.
The poll calendar
Four national surveys are scheduled to publish this week. BTG/Nexus releases a telephone poll on Tuesday, with fieldwork from Oct. 10 to Oct. 12. Quaest publishes Wednesday, based on 2,154 interviews with a margin of error of two percentage points. Datafolha publishes Thursday, with 2,520 interviews conducted Oct. 13 to Oct. 15. An online poll from Palver, with 5,000 respondents, also arrives Thursday. A televised debate is also scheduled for Thursday.
Flávio has led numerically in five of the six national runoff polls with fieldwork from Oct. 3 to Oct. 9, measured in valid votes. Datafolha's previous survey had him ahead 52% to 48% in valid votes, or 49% to 45% counting all votes.
What the price implies
At 87 cents, prices on both venues imply about a seven-in-eight chance for Flávio. That is consistent with a lead that has held across most pollsters.
Market implications
One reading is that Monday morning's gap was noise from a few Polymarket sellers, and the return to agreement confirms both venues are tracking the same polling picture.
A second reading is that the agreement is temporary. With four polls in three days, any survey showing Lula closing the gap could move one venue faster than the other, and the venues have different participants and settlement rules.
What to watch
The Quaest and Datafolha results and Thursday's debate will set the next move. Further debates follow on Oct. 18 and Oct. 23, before the vote on Oct. 25.