[quote=“libthinker, post:80, topic:45690”]
I have thought of the filibuster as being something somewhat outside of the constitution.[/quote]
It’s absolutely extraconstitutional, in the sense that the only thing the Constitution authorizes is for the Senate to make its rules. The filibuster is permitted under the rules of the Senate. Article I, Section 2 says that each House determines its rules.
My suspicion is that it originally came about as something to preserve comity in the senate, in the sense that if the minority found something to be truly a threat to their most basic interests, they had a last resort available.
My recollection from reading is that the filibuster isn’t really explicitly mentioned even in the rules. It is a side effect of the lack of a rule limiting debate: unlike Robert’s Rules (and the House Rules), the Senate must explicitly vote to close debate on an issue. The rules also call for a supermajority to reach cloture. The size of the supermajority has varied. It is currently 60%. There have always been privileged issues that had limited debate – budget reconciliation is the only one I can think of the top of my head.