Percentage of U.S. House and Senate members classified as moderate by DW-NOMINATE voting scores, 92nd–119th Congress (1971–2025). A "moderate" is defined as a member whose ideology score falls within 0.25 of center — neither strongly liberal nor strongly conservative. Both chambers decline along the same broad trajectory, though the Senate declined later and more gradually before converging with the House in the last decade.
Source: Voteview/Poole & Rosenthal, DW-NOMINATE Congressional Roll-Call Votes Database
(voteview.com), HSall_members.csv. Moderates defined as members with
|DW-NOMINATE dim1 score| < 0.25, the standard Voteview threshold; each point is calculated
directly from that Congress's member-level scores, not interpolated. Party-overlap finding:
Pew Research Center, "The Polarization in Today's Congress Has Roots That Go Back Decades"
(March 2022). 119th Congress figures are provisional (Congress still in session as of this
chart's last update).
Full methodology: sources.md |
Raw data: data.csv