How We Calculate the Flip Score

We use publicly available, official election results to estimate how competitive each U.S. House district is. The goal is transparency: you can see the sources, the math, and how each result is assembled.

Primary Data Sources

Election Results: MIT Election Data and Science Lab — U.S. House 1976–2024
Senate Results: MIT Election Data and Science Lab — U.S. Senate 1976–2020
Zip → Location: Zippopotam.us API
Location → District: Census Geocoder API
District Geometry: Census TIGERweb

Flip Score Formula

We calculate a two‑party margin using the latest general election results in each district. The flip score is a 0–100 scale where higher numbers indicate more competitive districts.

Margin
Two‑party margin in percentage points
100 − (2 × Margin)
Clamped to 0–100

Example: a 5‑point margin yields a flip score of 90. A 25‑point margin yields 50.

Senate Seats Up Next

Senate results are statewide, so we calculate competitiveness by state rather than district. We only show Senate seats that are up in the next election cycle (about 33–34 seats), using the most recent general election for that Senate class.

Why the Latest General Election

We use the most recent general election with valid two‑party totals so the score reflects current competitiveness. Special elections are excluded to avoid skew.

Notes on Accuracy

The flip score is a simplified measure meant for quick comparison. It does not account for redistricting changes, incumbency, fundraising, or local shifts. It is a guide, not a forecast.