information:classification
The two-track system, 60-vote rule and rise of the routine filibuster (1970 onward)

In 1977, during a filibuster on the Natural Gas Policy Act, the Senate set a series of precedents to restrict filibusters after cloture has been invoked. For instance, the Senate held that if cloture has been invoked on a measure, the presiding officer must take the initiative in ruling nongermane amendments out of order.: 286