Final answer:
In the U.S. Senate, a cloture motion requiring a 60-vote supermajority is used to end debate on a bill and is crucial for overcoming a filibuster. The practice allows the minority significant power in legislation, with the modern filibuster often only requiring the threat to prompt a cloture vote.
Step-by-step explanation:
The rule that allows three-fifths of the members in the U.S. Senate to set a time limit on debate over a given bill refers to the cloture motion used to end a filibuster. In the modern U.S. Senate, a supermajority of 60 senators must agree to invoke cloture to end the debate and proceed to a vote on the legislation. This supermajority requirement can be seen as a de facto measure for most legislation to pass, giving the minority significant power to obstruct a bill through prolonged debate or a filibuster. Historically, the use of the filibuster has evolved, with the traditional form seeing senators physically holding the floor for extended lengths of time. In recent practices, simply the threat of a filibuster is often enough to require the 60-vote supermajority, shifting the simple majority rule for passing a bill to a higher threshold. The filibuster is a tactic historically associated with extended debate, often to delay or block legislation, and is unique to the Senate. The classic filibuster could involve senators speaking for long durations, but today, merely indicating the intent to filibuster can prevent a bill from proceeding to a vote without a cloture motion. Rule changes have seen the requirement for cloture move from initially a two-thirds majority to the three-fifths (60 votes) standard of today, except for certain cases like judicial nominations and the budget reconciliation process which have different requirements.