Ideology in Congress, 1789–2026every member’s DW-NOMINATE position, one Congress at a time
speed½×1×2×4×drag the polarization chart to scrub · hover any dot for the member
How to read this. Each dot is one member of Congress, placed by DW-NOMINATE score: horizontal is the first dimension (economic liberal–conservative), vertical the second (region, slavery, civil rights — the issues that have divided parties internally). Members are matched across Congresses, so dots glide rather than jump; because an individual member’s position is nearly fixed over a career, the parties move mainly by replacement — dots fading in are freshmen, dots fading out are members leaving. Open circles mark each party’s mean position; the colored line trailing behind each circle traces that mean’s path over the previous 40 Congresses (80 years). Southern Democrats (teal) are Democrats from the eleven Confederate states plus Kentucky and Oklahoma — watch them sit apart from their party on the vertical dimension from the New Deal to the 1990s, then disappear. The bottom chart tracks polarization — the gap between the two major parties’ mean first-dimension scores — and doubles as a scrubber: drag it to move through time. (Its collapse and brief blank stretch in the early 1820s is the Era of Good Feelings: with the Federalists gone there was effectively one party, so there was no gap left to measure.) Hover any dot to identify the member; spacebar pauses, arrow keys step one Congress. Data: Lewis, Poole, Rosenthal, Boche, Rudkin & Sonnet, Voteview.com (HSall_members). Rebuilt from the original Voteview animation by Kyle Saunders, Sacred Cow BBQ — read the explainer essay.