What is the senate’s only defense to a filibuster?

To invoke cloture.

Explanation:

The filibuster is a political tactic or procedure employed by members of the Senate, wherein one or more members intentionally give long and often irrelevant speeches to debate a proposed piece of legislation, in order to delay or prevent the chamber from voting on a bill, an amendment, or motion,

When this happens, the Senate’s only defense to a filibuster is to invoke cloture, which is the only formal procedure to end a filibuster. However, only if three-fifths of the Senators vote in the affirmative, cloture is invoked.

Afterward, the Senate sets a series of conditions and constraints to end the debate such as only 30-Hour Time Cap to consider the bill, amendment or motion in question, and 1-hour time cap of debate per senator.

it was the first amendment

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