AFOS Tradeoff · USA-2026 midterms Political Risk Weekly

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United States·Issue3·Week of August 3-7, 2026·Published Monday 07:00 BRT
Signal of the week

The week of Aug 03 to Aug 07 broke the stillness that Issue №2 reported, and it broke in a specific way that matters more than the size of the move. In the contract that pays out if Democrats take the House, the price left Monday at 85.50% and closed Friday at 87.50%, a rise of 2.00pp. In the same contract, on the other side, the probability of Republicans controlling the House printed 13.50% on all five days, with no variation at all.

The two sides of the same contract should add up to something close to 100%. Over this week they went from 99.00% to 101.00%, because one side moved and the other did not. This is not a new reading on who wins the House: it is one leg of the book moving on its own, and the effect is that the price came to add up to more than the total that is possible.

The money tells the same story. In the Monday to Friday window, the Democratic side of the House took in USD 132 thousand of new volume and the Republican side took in USD 20 thousand, almost seven times less. Whoever traded during the week traded on one leg only.

In the Senate the behavior was the opposite, and the contrast is what gives the finding its meaning. Democrats rose from 44.50% to 45.50% and Republicans fell from 55.50% to 54.50%, a symmetrical move of 1.00pp on each side, with the sum of the two parked at 100.00% from start to finish. Same panel, same week, two contracts behaving differently.

On the side of those who measure voting intention, nothing moved, and for a reason that has to be stated: the polling base has not received a new reading since Aug 04. The house average for the generic ballot stands at D+5.66, across 29 polls from 23 pollsters in a 30 day window, and the distance between the highest and the lowest reading remains 9 points, from D+11 at Big Data Poll and Emerson College to D+2 at Reuters/Ipsos, RMG Research, McLaughlin and Harvard/Harris. The eight contracts this panel tracks hold USD 17.33M in total.

1.Executive Summary

House · Democrats
86.50%
+1.00pp since Aug 03
Probability of Democrats controlling the House, at today's capture. Over the week it rose from 85.50% to 87.50% while the Republican side stayed put, and on Aug 09 it reached 88.50%, the highest value in the series, which begins on Jul 29
Senate · Republicans
54.50%
-1.00pp on the week
Probability of Republicans controlling the Senate. It fell from 55.50% to 54.50% on the week, and here the other side gave ground by the same amount: the two add up to 100.00% from start to finish, unlike what happened in the House
Polls · House
D+5.66
9 points between the highest and the lowest
Democratic advantage in voting intention for the House. Simple arithmetic average of 29 polls from 23 pollsters over 30 days, unweighted and with no pollster excluded. The most recent field date in the base is Aug 04, so this yardstick has been still for six days

The week of Aug 03 to Aug 07 had movement, and the shape of the movement is the finding. In the House, the Democratic side rose 2.00pp and the Republican side did not budge by a hundredth over five days, which made the two sides of the same contract add up to 101.00%. In the Senate, both sides moved together and the sum stayed intact at 100.00%. Same panel, same week, two behaviors.

The second thing this issue reports is a loss of instrument, and it is declared here because it changes what can be written. The Senate seats contract, which in Issue №2 carried the scenarios section with its bands adding up to 99.20%, today adds up to 126.05%. The House seats contract is worse: between 17:11 and 18:17 today, a single band of it went from 40.55% to 10.50%. The market numbers in this issue are from Aug 10 at 18:24 UTC and cleared the capture guard, which takes two readings eight minutes apart and only releases them if they agree within 0.20pp.

2.Why this brief does not subtract the market from the poll

This brief publishes a poll average and never subtracts it from the market price. It looks like a technical detail and it is not: it is what separates a defensible reading from an invented number.

Two different quantities · why the subtraction does not exist
The calculation that is not done
86.50% minus D+5.66
The first number is a **probability**: the chance that one party ends up with the House majority. The second is a **vote margin**: how many percentage points separate the two parties in declared intention. Subtracting one from the other produces a number with no unit, which answers no question at all
The result of the subtraction **would change size** if the poll were expressed on another scale, without anything having changed in the world. A number that depends on the scale its input is written in is not a measurement, it is an artifact
**In 2012 Democrats won more votes for the House and fewer seats.** The distance between winning in votes and winning in seats can be entirely geography, that is, how the districts were drawn. Anyone subtracting the two measurements is treating that geography as if it were somebody's error
The comparison that is done
direction and conviction
Direction: whether the two measurements moved the same way or opposite ways. This week the House price moved toward the Democratic side and the poll average did not move, because no new poll entered the base after Aug 04
Conviction: whether one moved a lot while the other stood still. Here the answer carries a caveat that cannot be left out: the polling yardstick has been still for six days, so saying it 'did not react' would be false. It was not consulted, which is a different thing
Dispersion: the distance between pollsters, 9 points, remains larger than all the price movement of the week, which was 2.00pp in the largest case. Until that distance closes, the average is a fragile summary, and that is why this brief publishes the dispersion ahead of it

It is worth declaring what weakens this issue, and there are three things.

The first is the short House series, which begins on Jul 29 and is twelve days long. Any superlative about it is 'in the series', with the start date declared, never 'in the cycle'. When this issue says that 88.50% on Aug 09 is the highest value ever recorded, that holds for twelve days of collection, and does not describe the electoral cycle.

The second is the stalled polling yardstick. The most recent field date in the base is Aug 04. The average went from D+5.69 in Issue №2 to D+5.66, but the change did not come from a new poll: it came from the 30 day window rolling forward and dropping older polls out. When the composition of the set changes and voting intention is not measured again, calling that 'movement in the polls' is a reading error.

The third is the most serious and is detailed in the scenarios section: three of the five distribution markets this panel tracks got worse in quality over the week, and one of them is precisely the one that carried the previous issue's scenarios.

3.Weighted scenarios for the week

The scenarios below are not our narrative: they come from a contract that already prices every band of Republican Senate seats. Where in Brazil the hypothesis would have to be built, here it is enough to read what the market pays.

🔴 But this week the reading comes with a condition, and it has to come ahead of the numbers. The eleven bands add up to 126.05%, outside the 95% to 105% coherence gate this panel requires. In Issue №2, seven days ago, the same bands added up to 99.20% and passed. Bands adding up to more than 100% cannot be read as probability, because the excess is the margin of whoever runs the book. What is preserved is the shape of the distribution, not the level of each band.

So the numbers below appear normalized, divided by the raw sum of 126.05%, and the label changes with them: what follows is share of the book, never probability. The contract holds USD 2.80M.

📌 One rule of the American system changes the arithmetic: in a Senate tied 50 to 50, the tie breaking vote belongs to the vice president. That is why the 50 seat band counts on the Republican side.

Republicans hold the Senate · 51.61% share of the book

Adding the bands of 51 seats or more to the tie at 50, which the vice president's tie breaker resolves, the seats contract gives Republicans 51.61% normalized, on 65.05% raw. The heaviest individual bands on that side are exactly 50, at 12.69%, and exactly 51, at 12.30%, followed by 52, at 10.59%. It remains a narrow majority, not a comfortable one.

Democrats flip the Senate · 48.39% share of the book

The bands in which Republicans end up with 49 seats or fewer add up to 48.39% normalized, on 61.00% raw, and the heaviest of them is still 47 or fewer, at 27.37%, more than a quarter of the whole book concentrated in a single outcome. When this market imagines Democrats winning, it does not imagine a narrow win. 🔴 And the disagreement against the control contract, which gives Republicans 54.50%, stands at 2.89pp, against 4.80 points in Issue №2.

Tail · wide Republican majority, 16.03%

The bands of 53 seats or more add up to 16.03% normalized, on 20.20% raw. This is the tail that virtually no national poll would describe today, with the average at D+5.66, and it still has money behind it: the 54 seat band holds USD 771 thousand, the largest individual volume in the entire seats contract, despite showing a 4.64% share. High volume in a low share band is an old position left open, not conviction today.

4.Indicator Grid

ContractCurrentΔ weekVol USD acc.Implied reading
House · Democrats control86.50%+1.00pp since Aug 03USD 5.22MRose from 85.50% to 87.50% over the week and reached 88.50% on Aug 09, the highest value in the series that begins on Jul 29. Pulled back to 86.50% today
House · Republicans control12.50%-1.00pp since Aug 03USD 4.11MPrinted 13.50% on all five days of the week, without exception, and only moved on Aug 09, two days past the window. While it stood still, the two sides of the contract added up to 101.00%
Senate · Republicans control54.50%-1.00pp on the weekUSD 1.55MFell from 55.50% to 54.50% on Aug 05 and stayed. This contract's series begins on May 12 and has already run between 51.50% and 58.50%, so this is a small move inside a known range
Senate · Democrats control46.50%+1.00pp on the weekUSD 2.22MRose from 44.50% to 45.50% on Aug 07 and stands at 46.50% today. Unlike the House, here the other side gave ground by the same amount and the contract's sum stayed at 100.00% all week
Election happens as scheduled95.95%0.00ppUSD 0.31MA calendar contract, not a result contract. It serves as a floor: as long as it sits near 100%, the other seven are pricing an election that takes place
Senate · how many Republican seatssum 126.05%was 99.20% on Aug 03USD 2.80M🔴 Failed the 95% to 105% coherence gate. It passed seven days ago. It enters this issue normalized and labeled share of the book, never probability
House · how many Republican seatssum 127.90%was 110.90% on Aug 03USD 0.28M🔴 Failed and unstable: between 17:11 and 18:17 today, the 210 to 214 seat band went from 40.55% to 10.50%. It does not enter this issue in any form
Turnoutsum 96.40%was 91.40% on Aug 03USD 0.02MPassed the gate, and it is the only one that passes this round. It was failing from below in the previous issue. The heaviest band is 120 to 125 million votes, at 24.00%

5.Liquidity and market structure

The 8 midterm contracts tracked by this panel · vol. accumulated since openingUSD 17.33M
1House · who controlsDem 86.50%USD 9.33M
2Senate · who controlsRep 54.50%USD 3.77M
3Senate · how many seatsFAILED, sum 126.05%USD 2.80M
4Governorships · how manyFAILED, sum 165.95%USD 0.69M
5House · how many seatsFAILED, sum 127.90%USD 0.28M

6.Electoral calendar through November

DatePrintSampleWhy it matters
Aug 11State primaries, including Minnesotaprimary, not general electionThe Democratic Senate primary in Minnesota, between Angie Craig and Peggy Flanagan, features in this Monday's coverage. The panel does not price state primaries
Through AugustOther state primarieseach state has its own calendarThey do not enter this panel by estimate: each state has its own calendar and rules, and they are not in our base. When they enter, they enter with a source
Sep and OctNational trackersno mandatory registrationUnlike Brazil, there is no prior registration of polls in the United States. There is no print date to anticipate, only the cadence of whoever publishes
Nov 03Electionthe whole House, one third of the SenateThe date on which every contract in this panel settles

There is no equivalent to Brazil's TSE registry in the United States, so this calendar is the election's, not a poll publication schedule. The polls used by this brief come from an index that says which ones exist, and every number remains attributed to the pollster that produced it, with a link to the primary source. In this round, two of the 363 readings in the base had no primary source, both from John Zogby Strategies and both outside the 30 day window, so neither enters the average.

7.Watch list, week triggers

  1. The House rose on one side only, and that is where the money went. The Democratic side gained 2.00pp and USD 132 thousand of new volume on the week. The Republican side gained 0.00pp and USD 20 thousand. The two sides of the same contract came to add up to 101.00%. Watch whether the Republican side starts tracking again: it moved on Aug 09, outside the window, and the sum went back to 99.00%.
  2. The Senate seats book stopped adding up within one week. It summed 99.20% on Aug 03 and passed the coherence gate. Today it sums **126.05%**. The contract did not get smaller, it still holds USD 2.80M, so this is not abandonment: it is spread widening at the ends. While it lasts, the distribution can only be read as share of the book, and the cross check against the control contract loses precision.
  3. The House seats book became unreadable within one hour. Between 17:11 and 18:17 today, the 210 to 214 seat band went from 40.55% to 10.50%, an amplitude of 30 points, and the 225 to 229 band went from 27.15% to 7.15%. A book whose bands move 30 points in an hour describes no electoral outcome at all. It stays out of this issue and continues to be collected every day.
  4. The coherence gate switched sides within one week. In Issue №2 the Senate seats and the governorships passed, and turnout was failing from below, at 91.40%. Today **turnout is the only one that passes**, at 96.40%, and the other three failed from above. No election changed in that interval. What changed was the quality of the books, and that is what the gate is measuring.
  5. The polling yardstick has been still for six days. The most recent field date in the base is Aug 04. The average went from D+5.69 to **D+5.66**, and the variation is compositional: the 30 day window rolled forward and dropped older polls out, without a single new poll entering. Until the base gets a new reading, comparing the price to the poll compares a number from today with a number from last week.

8.Methodology

Market: Polymarket, read through the platform's own proxy, captured every 30 minutes and with a guaranteed daily point even when the price does not move, so the series records time and not only change. Every price quoted cleared the capture guard: two independent readings eight minutes apart, released only if they agree within 0.20pp. In this issue the two readings are from 18:16 and 18:24 UTC on Aug 10. ⚠️ A price reading meant for publication always bypasses the proxy cache. Without that the route returns the previous capture with an old timestamp, and the check ends up comparing a reading with itself. Polls: simple arithmetic average over a 30 day window, unweighted and with no pollster excluded, built from an index that says which polls exist, while every number remains attributed to whoever produced it. When the same pollster publishes more than one subsample of the same round, only one enters, by the hierarchy likely voters, registered voters, adults. Different rounds from the same pollster each enter, which is why the window holds 29 polls from 23 pollsters, selected out of 43 subsamples. ⚠️ The 9 point dispersion is measured over the 29 selected lines, not over the 43 raw subsamples. Over the subsamples it would look like 11 points, because it would include adult subsamples that the selection discards. Distributions: a distribution is only read as probability when its bands add up to between 95% and 105%. This round only turnout passes, at 96.40%. Senate seats (126.05%), House seats (127.90%), governorships (165.95%) and popular vote margin (152.25%) all failed. The Senate one enters normalized and with its label changed to share of the book, because its bands are exclusive and cover every outcome; the raw sum stays printed alongside, so the arithmetic remains checkable. The popular vote margin one stays out even normalized, because its bands overlap and one of them is 'any other outcome'. Book depth is not quoted: low liquidity on Polymarket does not mean the price is wrong, because the market is arbitraged continuously, and exposing that number produces a skewed reading. What this brief does not do: it does not forecast results, it does not say which measurement is right, and it does not issue investment advice.

9.Additional reading · macro coverage

Stories from the week in outlets on the AFOS fixed list. This brief is a primary source for market and polling data; what follows is context reading. Only links that resolve to the outlet's own site are included: of the 10 items collected on Aug 10, 7 had a canonical address and 3 existed only through the aggregator, with an address that does not resolve without a browser. Those 3 were left out, and the exclusion is declared here.

Mandatory disclaimer. This brief is observational research on the infrastructure of prediction markets, electoral polls, and news flow. Does not constitute investment recommendation. No position is recommended or implied. Polymarket is a USD-denominated market operating outside Brazilian jurisdiction; volumes mentioned are informative, not orientative. Portfolio decisions are the sole responsibility of the reader and must consider independent analysis, risk profile, and applicable regulation.
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AFOS Tradeoff · US · Issue №3 · The House rose without the other side giving ground, and the seats book stopped adding up | AFOS Analytics