The Byrd Rule, adopted in 1985, is a procedural constraint named after the late Senator Robert C. Byrd of West Virginia to prohibit “extraneous” provisions from being tacked onto reconciliation bills, which are fast-tracked budget packages that allow legislation to pass with a simple majority, bypassing the 60-vote filibuster threshold.

The U.S. Senate parliamentarian revealed on Sunday that a significant portion of the 2026 budget, known as "the big, beautiful bill," will require 60 votes to pass. Republicans had hoped to use the reconciliation process to side-step a filibuster,

Senate Parliamentarian Elizabeth MacDonough dealt big-time blows to GOP priorities this weekend when she ruled that chunks of President Trump's "big, beautiful bill" violate the chamber's rules. Why it matters: The so-called "Byrd bath" rulings further complicate Majority Leader John Thune's path to passing the mega tax and spending cut package by the White House's July 4 deadline.