Brazil votes on October 4, and the two polls published September 28 both have President Lula ahead in the first round by five points: 42% to 37% for Flavio Bolsonaro in BTG/Nexus, 39% to 34% in Quaest. Polymarket's "Brazil Presidential Election" market sees it the other way. As of 2026-09-29 13:07 UTC, Flavio's contract is at 58.05c (best bid 58c, best ask 58.1c) and Lula's is at 41.5c (best bid 41c, best ask 42c). Six weeks ago it was the reverse: in the August 16 report Lula was 65.5c and Flavio 28.75c. Numbers below are from the Gamma and CLOB APIs, fetched at that time.
01What the polls sayA first-round lead, and a runoff that is a coin flip
BTG/Nexus polled 2,000 voters by telephone on September 25-27 (margin of error 2 points) and Quaest, for Globo, polled 2,004 face to face on September 24-27 (also 2 points); both published September 28. In the runoff scenario BTG/Nexus has Lula 46%, Flavio 44%, and Quaest has them tied at 42%. An AtlasIntel/Bloomberg poll reported the same day by U.S. News had the runoff at 47.7% for Flavio and 47.6% for Lula. Per Rio Times coverage, both men are widely disliked, with rejection rates of 48-56% depending on the pollster.
Under Brazilian rules a candidate needs more than 50% of valid votes to win outright on October 4; otherwise the top two go to a runoff on October 25. With Lula at 39-42% and Flavio at 34-37%, the polls point to a second round, which is why the runoff numbers matter most. Polymarket's market resolves on who wins the presidency including any second round, per its rules, so the runoff polls are the relevant comparison.
02How the market flippedLula lost 14 cents in a month and never got them back
For the first week of September Lula's contract sat at 54.5-58.5c. It began to slip on September 8 (58.5c to 54.5c on the 6-hour prints), and the break came September 10, the day PoderData published a poll fielded September 6-9 (3,000 voters by telephone, margin 1.8 points) with Flavio ahead in the runoff 47% to 45%. PoderData had first shown him ahead, 45-44, on September 3; in mid-August Lula led the same series 46-45. On September 10 Lula's contract went from 51.5c at 12:00 UTC to 43.5c by 17:00 UTC, and Flavio passed him in the 18:00 UTC print, 53.8c to 43.5c. The market has not looked back since: Flavio has spent September 21-29 between 56c and 60.5c.
WIN PROBABILITY, 00:00 UTC PRINTS (SEP 29: 13:07 UTC)
Aug 31 Sep 8 Sep 11 Sep 29
Lula 55.5c 58.5c 45.5c 41.5c
Flavio Bols. 41.35c 39.85c 52.45c 58.05c
Gamma reports a 30-day change of -14c for Lula and +16.7c for Flavio; the last week has been quiet (+1c and -1.4c). The September 28 polls, which showed Lula's first-round lead widening, did not push the market back: Lula's contract printed 42.5c at 00:00 UTC on September 28 and is 41.5c today.
03Reading the bookWhy a five-point lead can trade at 41c
One reading of the gap is structural. A first-round lead does not win the presidency; the runoff does, and the runoff polls are level or, in AtlasIntel's case, a hair in Flavio's favor. If the market believes the final round is a toss-up and gives Flavio the edge on momentum (PoderData and Atlas), a price near 58c follows. That is an interpretation of what traders are paying for, not something the order book states.
What the book does show is conviction on each side. Flavio's is tight, with 28,240 shares bid at 58c against 2,368 offered at 58.1c. Lula's is a full cent wide, 10,882 shares bid at 41c and 152,853 offered at 42c, a lot of supply resting just above the last price. Over 24 hours Lula's contract traded $137,212 and Flavio's $151,318 - meaningful money for a market where the rest of the field (Haddad, Alckmin, Renan Santos and others) sits at a quarter of a cent or less.
04What would move it nextOctober 4, then possibly October 25
The next hard data is the first-round count on Sunday, October 4: whether Lula clears 50% (the polls say no), and by how much he leads Flavio. If the race goes to October 25, the runoff polls will be the story, since every recent one sits inside its own margin of error. Resolution follows the market's rules: the winner as indicated by a consensus of credible reporting, or the official result from Brazil's Superior Electoral Court if there is ambiguity, and "Other" if no result is known by June 30, 2027. Meanwhile polymarket-tui shows both contracts, their books, and a price chart side by side, so checking whether a poll release moved the ladder takes seconds.
$ uv tool install polymarket-tui
$ polymarket-tui
No account is needed to browse markets, books, and charts. The install page has Homebrew and one-liner options.