Senator and 2016 presidential hopeful Rand Paul (R-Ky.) invoked what his office described as a filibuster in the Senate Wednesday as lawmakers voted to renew the National Security Agency's (NSA) controversial bulk data collection program, which trawls millions of Americans' phone records.

"I've just taken the Senate floor to begin a filibuster of the Patriot Act renewal. It's time to end the NSA spying!" he wrote on Twitter.

News outlets have pointed out that Paul's speech is not technically a filibuster, since no specific bill is being delayed.

"The people don't want the bulk collection of their records, and if we were listening, we would hear that," Paul, who has been a vocal opponent of the practice, said on the floor in a speech that began Wednesday afternoon.

The controversial Patriot Act and it's provisions, like Section 215, which allows the NSA to sweep up Americans' phone records, is set to expire on June 1 unless Congress acts to renew it. Paul, whose libertarian political beliefs tend to skew against government intrusiveness, has previously said that he opposes the program and does not want it reauthorized. In a video he recorded two hours before he began his speech, Paul described his opposition to the Act and its renewal.

"I've chosen to filibuster the Patriot Act because the Patriot Act is the most unpatriotic of acts: it's unconstitutional, [and] it contravenes the Fourth Amendment, which says you have a right to privacy. The Patriot Act does not individualize warrants, it allows for general warrants, and it allows for a lower standard that can be used in our courts. This is very important, and I won't stand for the Senate to shove us aside and not debate this important issue."

Paul has become known for his use of the filibuster. In 2013, he spoke for almost 13 hours in protest of President Obama's drone program, giving rise to the social media hashtag, #StandwithRand, which his supporters still use.

The move comes as the NSA's controversial surveillance programs, which were exposed by the former NSA contractor Edward Snowden in 2013, are facing significant restructuring as Congress votes to renew them. Last week, the House overwhelmingly approved legislation––with bipartisan and White House support––that would curb the program. Under the new legislation, instead of bulk collection, the agency would rely on records stored by phone companies accessed via court order.

In the Senate, though, NSA programs face less certain opposition. Senate Majority Leader Mitch McConnell (R-Ky.), for example, supports renewing the existing program. Paul, on the other hand, is opposed to both renewing the programs as they stand, as well as the House measure to adjust them.

If it goes past midnight, Paul's speech, which was aided when he took questions from Sen. Ron Wyden (D-Ore.), could add another day to the legislative calendar and delay important votes. Members of Congress are scheduled to take Memorial Day leave on Thursday, but Paul's speech could throw that schedule off. Sen. Mike Lee (R-Utah) is also likely to help Paul by asking questions, NBC reports.

Regardless of how long he goes, the filibuster-like speech will gain Paul valuable media attention and clarify his stance on government surveillance and bulk collection. Other GOP candidates like Sens. Marco Rubio (R-Fla.) and Lindsey Graham (R-S.C.) favor renewing the Patriot Act in its current form.