The longest filibuster in US history was to block passing the Civil Rights Act. Guess which party did it?

The longest multi-speaker filibuster in the United States Senate was in 1964. It lasted 60 days according to the Senate’s website. Democrats in Southern states led the protest, while Northern Democrats did not support it.

The filibuster — a tactic in which senators delay voting on legislation by exercising their right to continuous debate — isn’t in the Constitution and wasn’t part of the Founding Fathers’ vision for the Senate. It was created inadvertently in the early 1800s and later became a popular tool for lawmakers to block legislation if a bill didn’t have enough support to go to a vote.

The record for the longest single-speaker filibuster is 24 hours, 18 minutes, and goes to former Sen. Strom Thurmond, a Republican from South Carolina in 1957, who also used the procedure to fight a civil rights bill.

The record for the longest multi-speaker filibuster is 60 days, and dates to 1964, when a group of Southern senators representing what used to be Confederate states attempted to stop the pending Civil Rights Act from passage after President John F. Kennedy’s assassination.

While Kennedy’s Democratic successor Lyndon Johnson urged Congress to pass the bill to end segregation and many other Democrats promoted it, a group of Democratic senators from the South filibustered to stop it, according to the Senate’s website.

The 60-day debate eventually ended on June 10, 1964, when it became clear that backers of the bill had enough votes to cut off debate. Forty-four Democrats and 27 Republicans voted for the bill to move to a vote. The Civil Rights Act of 1964 later passed into law with 73 yes votes, 46 of which were from Democrats, according to Senate records.

APNews fact checking.