Sen. Rand Paul waged an old-fashioned filibuster of CIA director nominee John O. Brennan Wednesday, taking to the floor for more than 12 hours to protest the Obama administration’s stance over whether the U.S. government can conduct targeted killings of suspected terrorists on U.S. soil.

“I just hope this won’t be swept under the rug,” Paul said just before he relinquished the floor early Thursday morning. “I would go another 12-hours, but I’ve discovered there are some limits to filibustering, and I have to take care of one those in just a few minutes here.”

When Paul yielded the floor, Assistant Majority Leader Richard J. Durbin, D-Ill., filed cloture on the Brennan nomination. Under Senate rules, the motion would require an intervening one day before the Senate could vote to limit debate on the Brennan nomination. That would set up a Saturday vote one hour after the Senate reconvenes, unless an agreement is reached to speed it up.

Senate Majority Leader Harry Reid, D-Nev., Thursday morning asked that he be recognized at 3 p.m. after the Senate Democrats and Republicans hold luncheons. Brennan does appear to have enough support to surmount the 60-vote threshold to invoke cloture and clear his nomination.

“I will speak until I can no longer speak,” the Kentucky Republican vowed as he began his effort shortly before noon. Under current Senate practice, a filibuster no longer requires continual speaking as it once did.

On Tuesday, Paul disclosed two letters he had received from the Obama administration in response to his questions over whether it has the power to conduct targeted killings on U.S. soil. Brennan answered that the CIA did not have that authority. Attorney General Eric H. Holder Jr. answered that there might be extraordinary circumstances, such as the 2001 terrorist attacks or Pearl Harbor, where the government might have that authority.

Paul was not pleased with Holder’s answer, and said the Obama administration still had not given a direct enough reply.

“I will not sit quietly and let him shred the Constitution,” Paul said Wednesday.

Several other senators, including Republicans Ted Cruz of Texas, Mike Lee of Utah and Marco Rubio of Florida and Democrat Ron Wyden of Oregon, joined Paul in the extended debate.

Senate Minority Leader Mitch McConnell, R-Ky., also announced he would oppose the Brennan nomination. “At whatever point we get to a cloture vote to extend debate on the nomination of Brennan, it is my view that cloture should not be invoked,” McConnell said. “This is a controversial nominee.”

Traditional filibusters are quite uncommon these days. In 2010, Sen. Bernard Sanders, I-Vt., spoke continuously for more than eight hours in protest of a tax cut deal.

Sarah Chacko and Scott Campbell contributed to this report.