Jessica Estepa

USA TODAY

Sen. Jeff Merkley spent 15 hours and 27 minutes speaking out against Supreme Court nominee Neil Gorsuch.

But that wasn't a filibuster.

Under Senate rules, a filibuster is a prolonged speech done to delay or block legislation or nominations. It's the tactic used in Mr. Smith Goes to Washington, when a bright-eyed Jimmy Stewart talks for a full day to keep an appropriations bill from moving forward.

While Merkley spoke for a long period of time, from Tuesday evening into Wednesday morning, it wasn't a filibuster because he wasn't actually delaying anything.

The key: Senate Majority Leader Mitch McConnell filed cloture on Tuesday night. Because McConnell already did this procedure, which would allow for a vote to move forward with Gorsuch's nomination, Merkley was simply holding the floor with his marathon speech.

The cloture rule was created back in 1917 as a way to end debate and used for the first time in 1919, when the Senate invoked it to end a filibuster on the Treaty of Versailles. In the decades afterward, that's how cloture was used: to end filibusters.

But nowadays, cloture is often filed at the beginning of the process on controversial bills or nominations, essentially ending unlimited debate before it can begin.

McConnell likely won't be able to get the necessary 60 votes for cloture, which would put the nuclear option on the table.