When did the 60-vote cloture rule originate and how has it changed (e.g., 1917, 1975)?

1. How a wartime change created a tool to stop filibusters — the 1917 origin story

The Senate adopted Rule XXII on March 8, 1917, during World War I to give the chamber a formal mechanism to cut off extended debate; the rule’s initial threshold required a two‑thirds supermajority of senators present and voting to invoke cloture. That innovation moved the Senate away from the ad hoc practices that had allowed prolonged obstruction and was first used in the postwar fight over the Treaty of Versailles in 1919. Modern accounts trace the procedural lineage from the 1917 adoption through decades of occasional cloture attempts, noting that the original two‑thirds requirement often made cloture difficult to achieve and therefore only sparingly effective in curbing filibusters ^{[1] [4]}.

2. The 1975 reform that made “60” the practical standard

In 1975 the Senate revised Rule XXII and replaced the two‑thirds benchmark with a formula requiring three‑fifths of senators duly chosen and sworn, which in a full 100‑member Senate translates to 60 votes. This change came after rising frustration in the 1960s and early 1970s over frequent cloture efforts and gridlock; the 1975 adjustment intentionally lowered the barrier to make cloture more achievable while preserving a supermajority safeguard for debate. Contemporary explanations emphasize that the rule’s wording — three‑fifths of those “duly chosen and sworn” — means the exact numeric threshold can vary with vacancies, but the political shorthand remains “60 votes” for a full Senate ^{[1] [3]}.

3. The 2010s “nuclear options” and the narrowing of cloture for nominations

While the 1975 change established the legislative 60‑vote norm, the Senate in the 2010s altered cloture for executive and judicial nominations through the so‑called “nuclear option.” In 2013 the Senate Democrats employed a majority vote to eliminate the 60‑vote threshold for most presidential nominations below the Supreme Court, and in 2017 Senate Republicans extended that change to Supreme Court nominations, making those nominations subject to a simple majority. Those moves did not eliminate the 60‑vote rule for ordinary legislation, but they narrowed cloture’s scope and reshaped confirmation politics by allowing majority control to bypass filibusters for many appointments ^{[1] [5]}.

4. What changed in practice — more filibusters, new tactics, and procedural workarounds

Histories and data note that after the 1975 reform the number and type of cloture motions increased dramatically, and filibuster tactics evolved from marathon floor speeches to “silent” or procedural” filibusters where mere threats or holds force cloture votes. Senators and scholars link the rise in cloture motions and obstruction to institutional changes like the two‑track system, which let the Senate work around floor hold‑ups but also incentivized more blocking strategies. The cumulative effect is that the 60‑vote threshold became a de facto supermajority requirement for major legislation, shifting bargaining dynamics and increasing the strategic value of the minority ^{[6] [3] [7]}.

5. Conflicting claims and the bottom line for readers

Some summaries compress the history and imply the “60‑vote rule” began in 1917; that is inaccurate: 1917 created cloture but not a 60‑vote standard — it set a two‑thirds requirement. The accurate sequence is adoption of cloture in 1917 (two‑thirds), a formal reduction to three‑fifths in 1975 (commonly 60 votes), and targeted major‑rule changes for nominations in the 2010s (simple majority) via the nuclear option. This reconstruction reconciles competing accounts and explains why popular shorthand sometimes confuses the 1917 origin with the 1975 numerical standard ^{[1] [2] [5]}.