2016 Postmortem
In reply to the discussion: Sanders Will Need 60 Votes To Pass Anything. But Hillary Clinton Will ONLY NEED 60. [View all]merrily
(45,251 posts)It started in 1917, with a 2/3 requirement, but there were fewer states then. They lowered the requirement to 3/5 in the 1970s.
https://en.wikipedia.org/wiki/Cloture#United_States
Filibuster of the Civil Rights Act of 1964 went on for, IIRC, 83 calendar days.
Off the top of my head, I can think of two reasons the super majority is needed more often now:
1. There seems to be less regard for the country and more for playing to the base.
2. There is no more requirement that Senators actually stand there and yammer. They just have to basically give notice of a filibuster and they're done. (Heaven forbid we demand that a Senator get tired while screwing up the country.)
More at the link above and at http://www.thenation.com/article/filibuster-faq-fact-fiction-and-why-we-need-reform/
BTW, karynnj has a very good grasp of Senate rules, as I recall.