In 1917, the US Senate voted to create a cloture process by which a two-thirds supermajority of senators present and voting could cut off a filibuster.
Notes on verification
Confirmed by Senate's own official records, CRS, Brookings, Brennan Center, and Pew Research, all corroborating the 1917 adoption of Rule XXII and its two-thirds threshold.
Sources
- The federal shutdown and the Senate filibuster: What could happen now? | Donald Trump News | Al Jazeera (aljazeera.com)
- https://www.brennancenter.org/our-work/research-reports/filibuster-explained (brennancenter.org)
- https://www.pewresearch.org/short-reads/2022/08/26/finding-60-votes-in-an-evenly-divided-senate-a-high-bar-but-not-an-impossible-one/ (pewresearch.org)
- https://www.brookings.edu/articles/what-is-the-senate-filibuster-and-what-would-it-take-to-eliminate-it/ (brookings.edu)
- https://www.senate.gov/artandhistory/history/common/briefing/Filibuster_Cloture.htm (senate.gov)
- https://www.senate.gov/about/powers-procedures/filibusters-cloture.htm (senate.gov)
- https://www.congress.gov/crs-product/R41342 (congress.gov)