Primary-to-general changes in 78 Washington races, 2014–2024
Do the 2022 and 2024 races behave like the longer historical sample?
The recent races had a narrower spread.
In the 19 races from 2022 and 2024, the middle 90% of changes in Republican vote share ran from −1.47 to +1.30 percentage points. For all 78 races from 2014–2024, the range was −4.82 to +3.05.
“Middle 90%” describes the span from the 5th to the 95th percentile in these past races. It is not a 90% probability range for this November. A one-point change means a share moving, for example, from 54% to 55%.
Charts from this investigation
Recent and earlier election changes
| Reference period | Races | Mean change | 5th percentile | 95th percentile |
|---|---|---|---|---|
| 2014–2024 | 78 | -0.36 | -4.82 | +3.05 |
| 2022 and 2024 | 19 | -0.02 | -1.47 | +1.30 |
The recent sample contains 19 races across two election years. These are historical percentiles, not probability bounds for November 2026.
Download all 78 races and the R reproduction script · Reference races (CSV) · Mean Republican-share change by year (CSV)
31st District examples in the broader historical panel
| Year | Office | Candidate followed | August share | November share | Change (points) |
|---|---|---|---|---|---|
| 2014 | House 2 | Christopher Hurst | 54.64% | 51.60% | -3.04 |
| 2016 | House 1 | Drew Stokesbary (R) | 73.98% | 71.59% | -2.39 |
| 2018 | House 1 | Drew Stokesbary (R) | 56.33% | 58.92% | +2.59 |
| 2024 | House 1 | Drew Stokesbary (R) | 63.86% | 63.69% | -0.17 |
Changes also varied by election year.
| Year | Races | Mean change in Republican share |
|---|---|---|
| 2010 | 44 | -1.54 points |
| 2014 | 53 | +0.42 points |
| 2016 | 34 | +0.80 points |
| 2018 | 51 | +0.83 points |
| 2020 | 45 | -0.91 points |
| 2022 | 32 | +0.59 points |
| 2024 | 43 | +0.68 points |
How the 78 races were selected
The code begins with 14 official primary and general-election files, totaling 4,369 rows. It matches the same two named candidates across August and November, producing 393 races. Of these, 302 pair a Republican and a Democrat. Exact name matching to earlier general-election winners identifies 213 races with an inferred incumbent, including 78 with a Republican incumbent.
The sample’s appointment history and boundary changes have not been fully checked. The recent subset shares only two election years. A different sample construction produced 96 races in the earlier investigation; that unresolved difference affects how representative these ranges may be.
Download source files, 78 races and reproduction code
Calculation and record checks · Return to the district results
Sources and production
Silphium is Penner Strategy’s research system. These studies use AI-assisted analysis and code-generated calculations and charts. The linked review records describe the calculation checks and remaining limitations.