CO-4 · House

The district, in brief

Colorado's 4th district encompasses the rural Eastern Plains and the southern Denver exurbs, including Castle Rock and Parker. The lines are not redrawn for 2026; the facts record the map as first used in 2022. The text gives no presidential results, but the facts carry a 2024 presidential baseline on the current lines.

The incumbent is Republican Lauren Boebert, elected to the 4th district with 53.6% of the vote in 2024 and unopposed in the Republican primary with 92,651 votes. The Democratic nominee is Eileen Laubacher, a retired United States Navy rear admiral and former U.S. National Security Council director, unopposed in her primary with 72,483 votes after four Democrats withdrew. One of them, Trisha Calvarese, the 2024 nominee, sued on March 2, 2026 to keep Laubacher out of the party caucus process, calling her a "lifelong Republican"; a judge denied a restraining order and Calvarese dropped out on April 1, 2026. As of June 30, 2026 Boebert had raised $1,010,297 with $247,201 on hand; Laubacher $10,349,940 with $3,610,909 on hand.

On September 17, 2026 an ethics complaint was filed against Boebert with the House Ethics Committee alleging affairs with three staffers and a payment of roughly $200,000 to prevent the complaint; no investigation has been launched and Boebert denies the allegations. Every rater listed calls the seat R: Decision Desk HQ (July 14, 2026), the Cook Political Report (February 6, 2025), Inside Elections (March 7, 2025), Sabato's Crystal Ball (July 30, 2026) and The Economist (May 6, 2026). The text records no district polls.

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: No presidential results in the text; the facts carry a 2024 presidential baseline on the current lines but the text does not state it.; No district polls in the text; the model's basis also says no district polls.; Endorsement sections are empty; no endorsements are named for either nominee.; The ethics complaint is described only as filed; the text records no committee action.; No general-election ratings finer than 'R' are given (no Lean/Likely/Safe).

Read from the district's section of Wikipedia's state page (CC BY-SA), archived as 8bb7a50842a1; 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.

Who holds the seat now

Lauren Boebert (Republican), in this chamber since 2021, 3 terms. Committees: House Committee on Natural Resources; House Committee on Oversight and Government Reform.

From the congress-legislators dataset (CC0), archived as ae8cb9477c48. For a Senate race this lists both of the state's senators; the one whose term ends in the election year holds the seat on the ballot. For a House district redrawn for 2026 it is the member elected under the old lines with this number, who may be running elsewhere; the dossier above names who is running here.

How it has voted for president

A shift of 9.9 points toward the Democrats from 2016 to 2024. county returns placed on the current lines by 2020 block population; 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.

Who are the voters?

Of about 494,333 adults 25 and over. In 2020 the district voted 40.6% Democratic (two-party) for president. With the same preferences and a 2022-style midterm turnout, it would vote 41.5% Democratic: the midterm electorate alone moves the margin 1.9 points toward Democrats. Group shares are estimated from how results vary across the state's census tracts (ecological inference, anchored to Pew's 2020 validated-voter figures) and calibrated to this district's actual 2020 vote; turnout is the Census survey's state rate by race and national rate by education, whose state samples carry margins of several points.

Not answered here: how each group will vote in 2026. These are 2020 preferences; this profile is description, not yet an input to the forecast.

The money

FEC bulk candidate summaries through September 30, 2026; $5,956 of independent expenditures for or against these candidates this cycle (FEC Schedule E, types 24E and 24A), which is the parties' and outside groups' own revealed view of whether this seat is in play.

The district in numbers

ACS 5-year 2023, the Census Bureau's own tabulation of this district (118th Congress lines). Unemployment is the BLS county series placed on the district by block population, not seasonally adjusted, so changes are same-month comparisons. Income, transfers and jobs are BEA county accounts placed the same way, compared with the average district. Every other figure is a named column of a named table in the Bureau's summary file, archived before it was read. This is what a reader knows about a district before looking at a poll; the model does not yet use it, and whether it should is a registered question.

Who is favoured, and by how much?

The 90% interval runs from -25.4 to +2.8 points, D-R. It is wide because this district has never been polled.

What is this built on?

A model trained on every contested House race 2012-2024 predicts this district's lean from its own record: presidential and House results on the current lines, incumbency, both candidates' prior offices, outside and party money before 1 October, demographics and public-assistance shares from the Census release before the election, local unemployment and income, and religious tradition. The national margin comes from presidential approval, the economy, the midterm penalty and the generic ballot corrected for its measured lean. Draws share national and state errors, so the seat total and this district come from the same simulation.

Not answered here: district polls, which are not yet folded in.

Why does the model say this?

Each figure is how far this district's predicted lean moves when that one feature is set to the typical value across 2026 districts, everything else held: 2024 presidential lean (R+17.2): 5.8 pts toward the Republican; 2024 House lean (R+9.4): 2.2 pts toward the Republican; experience gap (-4 levels, D minus R): 1.6 pts toward the Republican; median hh income ($116,031): 0.7 pts toward the Republican; presidential trend 2020-24 (D+6.3): 0.4 pts toward the Democrat.

How sure is it, and of what?

Total sd 8.54 points, made of the seat's own volatility 89%, correlated polling error 11%. The decomposition is stored with the forecast rather than reconstructed, so a probability whose dominant input is a placeholder is visibly that.

Not answered here: a nowcast. 'If ballots were cast today' needs something that observes today, and for a House district nothing does. Publishing the election-day figure under both labels would make one forecast look like two.

How was this number made?

Run 6f211e6f-2bdc-4dda-8f72-81fc628dab0b, house_district_prior/0.2.0, as of 2026-10-02. Promoted by a pre-registered gate: on 2016-2022 its Brier score was 0.036 against 0.049 for the previous method, and on a single 2024 run 0.023 against 0.032 (experiments/district_gate_result.md, with an independent review).