A Promised Land by Barack Obama:
The filibuster isn’t mentioned anywhere in the Constitution. Instead, it came into being by happenstance: In 1805, Vice President Aaron Burr urged the Senate to eliminate the “motion to proceed”—a standard parliamentary provision that allows a simple majority of any legislature to end debate on a piece of business and call for a vote. (Burr, who seems never to have developed the habit of thinking things through, reportedly considered the rule a waste of time.)
It didn’t take long for senators to figure out that without a formal way to end debate, any one of them could bring Senate business to a halt—and thereby extract all sorts of concessions from frustrated colleagues—simply by talking endlessly and refusing to surrender the floor. In 1917, the Senate curbed the practice by adopting “cloture,” allowing a vote of two-thirds of senators present to end a filibuster. For the next fifty years the filibuster was used only sparingly—most notably by southern Democrats attempting to block anti-lynching and fair-employment bills or other legislation that threatened to shake up Jim Crow. Gradually, though, the filibuster became more routinized and easier to maintain, making it a more potent weapon, a means for the minority party to get its way. The mere threat of a filibuster was often enough to derail a piece of legislation. By the 1990s, as battle lines between Republicans and Democrats hardened, whichever party was in the minority could—and would—block any bill not to their liking, so long as they remained unified and had at least the 41 votes needed to keep a filibuster from behing overridden.
Without any constitutional basis, public debate, or even the knowledge of most Americans, passing legislation through Congress had come to effectively require 60 votes in the Senate, or what was often referred to as a “supermajority.” By the time I was elected president, the filibuster had become so thoroughly integrated into Senate practice—viewed as as essential and time-honored tradition—that nobody much bothered to discuss the possibility of reforming or doing away with it altogether.