Update (1/17/2018, 2:25pm ET): The Senate broke the filibuster by a vote of 60-38 after just two-and-a-half hours of discussion Tuesday evening. This limits the debate on the FISA Amendments Reauthorization Act to a maximum of 30 hours. According to Rand Paul's press liaison it is "highly likely" the vote will occur Wednesday night or sometime on Thursday. Motherboard will update this post with the results.

On Tuesday afternoon, a bipartisan coalition of 3 Democrats and 2 Republicans committed to filibustering the FISA Amendments Reauthorization Act of 2017, a bill that effectively expands the warrantless surveillance of American citizens. Last week, the House of Representatives voted in favor of a nearly identical bill to the one being considered in the Senate today.

The filibuster coalition is led by Republican Senator Rand Paul and Democratic Senator Ron Wyden, who have co-sponsored the USA Rights Act, a privacy-oriented alternative to the FISA Amendments Reauthorization Act that is widely supported by civil rights groups.

The USA Rights Act would require strong oversight of intelligence agencies by an independent agency, require intelligence agencies to get a warrant to read the communications of US citizens, and make a far-reaching type of surveillance known as “about collection” illegal.

“A bill of this importance ought to be open to a real Senate debate, not blast through the Senate on the most extreme procedure with no amendments, no discussion, our way or the highway,” Wyden said during the press conference.

Read More: Why the Vote on FISA Section 702 Matters

A filibuster is a tactic for delaying a vote indefinitely that basically involves senators refusing to stop talking. In the past, senators have gone to absurd lengths to extend a filibuster, such as reading Shakespeare and recipes to the Senate. A filibuster can only be ended by a two-thirds majority vote, known as cloture.

If the opposition cannot obtain a two-thirds vote to end the filibuster, that means they will have to reach a compromise on a new FISA reauthorization bill.

FISA is set to expire on January 19 unless it is reauthorized by Congress, although the surveillance practices it allows will continue through April as a result of a legal review process by intelligence agencies that authorizes the surveillance practices on an annual basis.

This gives Congress about three months to reach a compromise on a new FISA reauthorization bill that will hopefully protect the electronic communications of Americans from warrantless surveillance.

The Senate is scheduled to begin discussing the FISA reauthorization at 4:30 PM Eastern time. Motherboard will update this post if cloture is reached.

What is FISA?

The Foreign Intelligence Surveillance Act was enacted in 1978, but in 2008 it was amended with Section 702, which allows US intelligence agencies to spy on any foreigner outside the US without a warrant. On a number of occasions, however, US intelligence agencies exploited FISA loopholes in order to spy on the electronic communications of American citizens without a warrant.

The FISA reauthorization bill passed by the House and being considered by the Senate are specifically focused on Section 702 and preclude any protections against the loopholes that allow government agencies to spy on Americans without a warrant. The first loophole, known as “backdoor search,” allows intelligence agencies to read the electronic communications of any American in contact with a foreigner that the agency had deemed a target.

The second loophole is known as “about collection” and allowed intelligence agencies to surveil any American whose electronic communications included information about a foreign target, such as their email or phone number, even if that American wasn’t in contact with the foreign target. This practice was voluntarily abandoned by the NSA in 2017 after it came under scrutiny by the Foreign Intelligence Surveillance Court.