Final answer:
A filibuster is a procedural tactic used in the U.S. Senate to extend debate and block legislation. It is not mentioned in the Constitution but has become an important part of Senate procedure, often requiring a supermajority to end debate and move forward with voting.
Step-by-step explanation:
The term filibuster refers to the practice where a Senator or a group of Senators extend the debate over a legislation indefinitely, mainly as a strategy to block or delay a bill's passage. The Constitution does not explicitly mention the filibuster; however, it is a procedural tactic that has emerged within the rules of the U.S. Senate, exploiting the tradition of unlimited debate. One historical example includes the case where Senator Strom Thurmond held the record for the longest filibuster, notably opposing the Civil Rights Act.
Over time, the filibuster has evolved. Today, instead of holding the floor with prolonged speech, a simple declaration of filibustering can postpone a vote indefinitely unless 60 Senators vote for cloture to end the debate. This modern use of the filibuster effectively raises the threshold for legislation to pass from a simple majority to a supermajority of 60 votes, granting significant power to the Senate minority.
While the filibuster is not in the Constitution, the concept of free debate is, emphasizing the Framers' intent for open political discourse; although, the practice has developed into a powerful legislative tool that can significantly affect the passing of laws.