Party Loyalty: Methodology

A deterministic percentage derived from Tier-1 (government) vote records. No editorial input.

What this figure is — and isn't

Party loyalty is a count, not a characterisation. It answers one arithmetic question: on recorded votes where this member’s party had a clear majority position, how often did they vote with that majority?

A high percentage is not labelled “partisan” and a low percentage is not labelled “independent.” The platform asserts the formula and the inputs — never a verdict about a person’s ideology or character.

Source data

All inputs are Tier-1 government records (Congress.gov roll-call votes). No news articles, no third-party ratings, no community submissions enter the calculation.

Party affiliation is the canonical party stored on the member’s profile, backfilled from the congress-legislators dataset. Currently supported: Democrat and Republican.

Algorithm

For each roll call where the member cast a vote:

Count party votes. Among all members sharing this person’s party, count how many voted “for” and how many voted “against.” Abstain / present / not-voted are excluded from the count.
Determine the party majority position. If more party members voted “for” than “against,” the party majority = “for.” Ties are excluded — a split party has no majority position and the roll call does not count toward this member’s percentage.
Check alignment. If the member’s vote matches the party majority, it is counted as aligned.

party loyalty % = aligned votes / qualifying roll calls × 100

Qualifying = roll calls where (a) the member voted for/against and (b) the party had a clear majority (no tie). The member’s own vote is excluded from the party count — only other party members are counted — so the member cannot move their own majority position.

Minimum data requirement

The figure is withheld until at least 20 qualifying roll calls exist. Below this threshold the sample is too small to be meaningful, and no percentage is displayed.

What the figure does not measure

It does not measure ideological position (left/right/center).
It does not distinguish procedural votes from substantive policy votes.
It does not account for whether the member sponsored or opposed the underlying bill.
It is not a rating, score, or endorsement by this platform.

Reproducibility

The underlying vote records are sourced from Congress.gov via the public API and stored in our database. Every vote row links to its source, visible on the member’s Voting Record tab. The formula above is applied directly to those rows — no intermediate ratings or curated datasets.