Using a filibuster to delay or block legislative action started happening in the 1850s, and it became a powerful tool to protect the rights of the minority party and to promote compromise.

A filibuster works like this: If at least 41 of the 100 senators are in strong opposition to a piece of law or a nominee, they can vote to continue talking and debating and block a final vote on the issue. A final vote can only be taken if and when the majority wins 60 senators' votes. This two-thirds, majority vote to end a filibuster is called "cloture."