Iowa · Governor

Who is running?

Rob Sand (Democratic), Zach Lahn (Republican). The margin below is Rob Sand minus the other candidate in the main contest; the rest are on the ballot and not in it.

The race, in brief

Iowa elects a governor on November 3, 2026, with Republican Kim Reynolds not seeking a third term; it is the first open governor's race since 2006, the last one Democrats won. The text calls Iowa a red state: Republicans control the legislature, hold all 4 U.S. House seats and have won every Senate race since 2010, and Iowa has voted Republican for president since 2016.

The Republican nominee is businessman Zach Lahn, running with state representative Derek Wulf; he won the June 2 primary in an upset with 37.65% over Randy Feenstra, whom Donald Trump had endorsed. The Democratic nominee is state auditor Rob Sand, the only Democrat on the ballot, running with Crawford County supervisor Dave Muhlbauer. The Des Moines Register has reported that Lahn lived in Kansas until 2023 and spent 75 nights in Wichita between October 2025 and spring 2026, and that the Black Hawk County Sheriff's Office is investigating Wulf for theft and fraud; Republicans including Reynolds accuse Sand of using audits to raise his profile.

Cook, Decision Desk HQ, Fox News, Inside Elections, Sabato's Crystal Ball and Silver Bulletin list the race as 'Flip'; RealClearPolitics lists Tossup (June 5, 2026). The aggregate polling average is Sand 50.0%, Lahn 43.0%. Recent polls include Marist University, September 17–20, Sand 54% to 42% among registered voters; co/efficient (R), September 14–16, 46% to 42%; and Cygnal (R), September 9–11, 48% to 44%.

A paragraph quoting a model forecast from the day this brief was written is omitted; the current forecast is at the top of this page.

The facts, each beside its sentence

Not in the source: The forecast rows in facts carry no basis field, so the dossier cannot say what the model's numbers stand on (for example, whether the statewide polls in the text are in it).; The ratings table gives only the party letter or 'Tossup'/'Flip'; no Lean/Likely/Safe strength is given. The text does not say which way 'Flip' points or how strongly.; The text gives no fundraising for either nominee.; The text gives no presidential or previous gubernatorial vote shares for Iowa.; Endorsement sections are empty in the text.

Read from the district's section of Wikipedia's state page (CC BY-SA), archived as b8c232b1fe4d; written by claude-fable-5-1 (batch reader) on 2026-09-30 and checked mechanically: every quote occurs verbatim in the archived text, every number in the brief occurs in the inputs. No probability here is the reader's.

How it has voted for president

A shift of 3.3 points toward the Republicans from 2016 to 2024. county returns summed; MEDSL county file (2016), an MIT-licensed county file (2020, checked against certified state results) and MEDSL precinct returns (2024). For a district split across counties this is an estimate, and where the state published the exact 2024 figure for these lines, that exact figure is the one the model uses.

The state in numbers

ACS 5-year state tables; BLS county unemployment and BEA county income, transfers and jobs summed to the state. Every figure is a named column of a named public-domain table, archived before it was read.

Who is ahead, and by how much?

Two numbers because they answer two questions. The nowcast is where opinion stands; the election-day forecast is where it is likely to end up.

How likely is each to win?

Monte Carlo error is ±0.2 points. A change smaller than that is simulation noise rather than news, and this page will not describe it as movement.

How wide is the range?

Nowcast: 90% of simulations fall between -3.9 and +14.7 points. Election day: -7.3 to +15.2. The election-day interval is 3.9 points wider, which is the 33 days of movement still to come.

What is the uncertainty made of?

Total sd 7.16 points, made of race-specific polling error 48%, drift to election day 32%, correlated polling error 12%, latent opinion 9%. The decomposition is stored with the forecast rather than reconstructed, so a probability whose dominant input is a placeholder is visibly that.

What evidence is this built on?

11 polls, most recent 2026-09-20. 55% verified against a primary source.

What changed since the last run?

Shaded band is the 90% interval, line is the central estimate, positive is Rob Sand ahead of Zach Lahn. Over 15 stored forecasts the central estimate moved -2.8 points. There were 7 specification changes (marked on the axis) and no new polls arrived over this window — so every movement in this chart is a change to the model, not a change in the race.

Since 2026-10-01: margin +0.00 points, win probability +0.0 points, on +0 polls. Of that, +0.00 points came from +0 poll(s), -0.00 from the shorter horizon, and +0.00 from the model specification.

How has this model done before?

Measured on 230 forecasts across 230 races in cycles 2016,2018,2020,2022,2024: mean absolute error 4.56 points, Brier score 0.0543. The nominal 90% interval contained the result 94% of the time, the 80% interval 84%, and the 50% interval 47%. Read that with care: a national polling miss moves every race in a cycle at once, so the sample size for a question about the intervals is 5 cycle(s), not 230 forecasts. Per cycle -- bias +1.644 pts; 2016: n=43 bias=+4.68 cov90=0.860; 2018: n=63 bias=-0.52 cov90=1.000; 2020: n=35 bias=+5.44 cov90=0.886; 2022: n=54 bias=-0.60 cov90=0.944; 2024: n=35 bias=+1.48 cov90=1.000.

Where did every number come from?

Nowcast run 69e38b74-f048-4495-9262-152b20ec36fc and election-day run be3a9abd-f88d-412a-b3d9-0e2a8deb11b8, model single_race_latent/0.8.1 at commit bdf7e83107c17a2399efe61a44ef1bbee48f9284, seeds 20260924 and 20260924.