Nearly 13 hours after he started, Sen. Rand Paul, R-Ky., ended a dramatic, old-fashioned filibuster early Thursday morning -- having held the floor for most of the day and night to rail against the administration's drone program while holding up the nomination of John Brennan for CIA director.

Business in the Senate ground to a halt Wednesday as Paul, aided by colleagues from both parties, launched into the filibuster as he challenged the president’s authority to kill Americans with drones.

Paul's filibuster was longer than most in U.S. history, as most flame out by the 10-hour mark. Paul finished speaking around 12:40 a.m. local time, and his filibuster lasted 12 hours and 52 minutes.

"My legs hurt. My feet hurt. Everything hurts right now," Paul told Fox News shortly after stepping off the Senate floor, saying he believes "we did the best that we could."

"I would be surprised if we didn’t hear back from the White House," Paul said.

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Watch Paul discuss his filibuster on Fox News at 2:05 p.m. ET on Thursday.

In a show of support, Republican Senate Minority Leader Mitch McConnell came to the Senate floor and congratulated Paul for his "tenacity and for his conviction." McConnell also called Obama's choice of Brennan a "controversial nominee."

The late Rep. Strom Thurmond holds the record for the longest filibuster, at more than 24 hours.

Paul is one of several lawmakers -- on both sides of the aisle -- who has raised concerns about the legal justification for launching drone strikes against Americans overseas. But Paul took to the floor after receiving a statement from Attorney General Eric Holder that creaked open the door to the possibility of using a drone to kill an American inside the United States.

“To allow one man to accuse you in secret -- you never get notified you've been accused,” Paul said on the floor. “Your notification is the buzz of propellers on the drone as it flies overhead in the seconds before you're killed. Is that what we really want from our government?”

Paul said he’d be raising the same complaints under a Republican president.

“No one politician should be allowed to judge the guilt, to charge an individual, to judge the guilt of an individual and to execute an individual. It goes against everything that we fundamentally believe in our country,” he said.

The senator, speaking for hours, was later joined by Democratic Sen. Ron Wyden of Oregon, as well as fellow Republican senators -- all of whom dragged out the filibuster by asking Paul lengthy and drawn-out questions. At one point, after the filibuster neared it's eleventh hour, Sen. Ted Cruz of Texas began reading numerous Tweets in favor of Paul.

That tactic allowed Paul to take brief breaks -- which included a snack break when the senator ate a Milky Way candy bar -- before resuming his speech.

Senate Majority Leader Harry Reid briefly interrupted to ask Paul if he planned to allow a vote to end debate. When Paul said he wouldn't, Reid concluded that other senators should acknowledge that their work for the day is "through" and plan to come back Thursday.

Paul, who started speaking shortly before noon, said he will filibuster Brennan's nomination “until I can no longer speak,” though he later suggested he would back down if he received a written assurance from Attorney General Eric Holder that the administration would not carry out drone strikes on noncombatant Americans.

This kind of filibuster is rare – typically, senators “filibuster” by refusing to grant the majority the 60 votes needed to proceed to a final vote on certain bills.

Paul, though, said he wanted to raise the “alarm” about the drone issue.

He spoke after receiving letters from Holder on drone authority.

In one letter, Holder said the U.S. has never carried out a drone strike against one of its citizens on American soil, and called a situation where such a strike may occur "entirely hypothetical" and "unlikely to occur."

However, Holder did not entirely rule out that such a scenario may occur in the future, and indicated that such a strike would be legal under the Constitution.

“It is possible, I suppose, to imagine an extraordinary circumstance in which it would be necessary and appropriate under the Constitution and applicable laws of the United States for the president to authorize the military to use lethal force within the territory of the United States," Holder said.

Holder said "catastrophic" attacks such as the Sept. 11 attacks or the attack on Pearl Harbor are examples of circumstances where the president could conceivably feel such an action is necessary.

Testifying on Capitol Hill on Wednesday, Holder agreed that it would be unconstitutional to use a drone on American soil against a U.S. citizen and suspected terrorist who did not pose an imminent threat.

Brennan has been a staunch supporter of the administration’s drone program. But, after members of the Senate Intelligence Committee extracted key documents on the program from the administration, the panel on Tuesday voted 12-3 to approve the nomination.

Fox News' Chad Pergram contributed to this report.