By a vote of 63-34, the Senate confirmed John Brennan as director of the CIA on Thursday. (The Washington Post)

Sen. Rand Paul (R-Ky.) forced Washington slightly off its axis Thursday after he filibustered President Obama’s pick to head the CIA. The rare “talking filibuster” generated extraordinary scrutiny of the Obama administration’s drone-strike program and revealed some surprising divisions and alliances on Capitol Hill over the president’s anti-
terrorism tactics overseas.

The filibuster culminated in the Senate confirmation of John O. Brennan to be director of the CIA by a vote of 63 to 34. But it scrambled the usual partisan landscape in the Capitol, with some Republican lawmakers attacking Paul for criticizing the president, while liberals and Democrats praised him. Of the 81 votes to end the filibuster, 28 were from Republicans, 13 of whom also voted to confirm Brennan.

The filibuster began Wednesday afternoon and lasted for nearly 13 hours, ending after midnight on Thursday. Paul was demanding that the White House clarify that it would not use aerial drones on U.S. soil to kill American citizens suspected of terrorism — a point on which he felt the administration had not been sufficiently clear.

Brennan’s nomination forced the administration to be more forthcoming about its secretive drone operations, which have devastated al-Qaeda’s core leadership in Pakistan and have been expanded to target affiliated groups in Yemen and Somalia.

Sen. Lindsey O. Graham (R-S.C.), one of the administration’s harshest Republican critics but a supporter of the drone program, said the filibuster caused him to change his vote on the Brennan nomination to support Obama.

“I am going to vote for Brennan now because it’s become a referendum on the drone program,” Graham said. “Where were all these people during the Bush administration?”

The one Democrat who joined the filibuster, Sen. Ron Wyden (Ore.), said that Paul was asking important questions of the administration.

“I want it understood that I have great respect for this effort to really ask these kinds of questions,” Wyden said. “And Senator Paul has certainly been digging into these issues in great detail.”

The American Civil Liberties Union issued a statement supporting Paul. “There is now a truly bipartisan coalition in Congress and among the public demanding that President Obama turn over the legal opinions claiming the authority to kill people far from a battlefield, including American citizens,” said Laura W. Murphy, director of the ACLU’s Washington Legislative Office.

Brennan, a CIA veteran and former station chief in Saudi Arabia, has served as Obama’s principal counterterrorism adviser for the past four years and one of the chief architects of the program that has emerged as the spy agency’s signature counterterrorism tactic. The Brennan nomination brought unprecedented scrutiny to the administration’s use of drones to kill terrorist suspects overseas, and in recent days critics have questioned whether it could be imported to the United States to target American terrorism suspects at home.

A still-theoretical discussion about the domestic use of armed drones emerged in recent days from congressional demands to review Justice Department legal opinions that justified the 2011 drone killing in Yemen of Anwar al-Awlaki, a U.S. citizen.

The Obama administration turned over a number of classified memos to the Senate Intelligence Committee that laid out the legal rationale underpinning the joint CIA-military operation against Awlaki, who was described by intelligence officials as a senior operational figure in al-Qaeda’s Yemen affiliate.

In a letter to Paul on Monday, Attorney General Eric H. Holder Jr. said that in an “extraordinary circumstance” such as the Sept. 11, 2001, attacks or the 1941 Japanese bombing of Pearl Harbor, it might be “necessary and appropriate” for the president to authorize the military to use lethal force in the United States. But Holder said such a situation was “entirely hypothetical.”

Paul was not satisfied.

White House spokesman Jay Carney said Thursday that “the president has not and would not use drone strikes against American citizens on American soil.”

“On the broader question, the legal authorities that exist to use lethal force are bound by and constrained by the law and the Constitution,” Carney continued. “The issue here isn’t the technology. The method does not change the law. The president swore an oath to uphold the Constitution and he is bound by the law. Whether the lethal force in question is a drone strike or a gunshot, the law and the Constitution apply in the same way.”

Holder also sent a second, brief letter to Paul: “It has come to my attention that you have now asked an additional question: ‘Does the president have the authority to use a weaponized drone to kill an American not engaged in combat on American soil?’ ” Holder wrote.

“The answer to that question is no.”

Paul said he was satisfied with the answer, although it still leaves open the possibility that a drone strike could be used against an American who was engaged in combat on American soil.

Even as Paul eventually got what he wanted, his filibuster divided his party between the new generation of tea party-affiliated Republicans and the older generation of foreign policy hawks.

Perhaps the two most prominent hawks, Graham and John McCain (R-Ariz.), took to the Senate floor Thursday to denounce Paul’s quest.

They offered a robust defense of antiterrorism policies that began in the George W. Bush administration and had been warmly embraced by almost every congressional Republican, particularly the two leading GOP senators, Minority Leader Mitch McConnell (Ky.) and Minority Whip John Cornyn (Tex.).

McCain said he was upset by Paul’s assertions that the Obama administration was leaving itself or a future administration the authority to attack a U.S. citizen who was a high-profile protester, such as actress Jane Fonda, whose opposition to the Vietnam War rankled the Nixon White House.

“To somehow think that under present circumstances, we would have killed Jane Fonda, that’s so ridiculous there’s no way to respond to it. It’s just an insult to your intelligence,” McCain told reporters Thursday.

Paul told reporters that there is now a “healthy debate” in GOP circles over the methods used in national security.

“It used to be monolithic that, whoever is in the country that we think is bad, we call them ‘enemy combatants,’ lock ’em up, throw away the key. . . . People are starting to understand that just by calling them an enemy combatant doesn’t make them an enemy combatant,” he said.

Paul said the filibuster was not planned. He had enough time for his staff to put together binders of information for him, but he didn’t make other special preparations.

He also said that the support of his colleagues — more than a dozen of them took part in the filibuster, including Democrat Wyden — was mostly not coordinated.

Some said that their participation was the result of being caught up in the drama of the moment. “I, like everybody else, was sort of inspired by Senator Paul’s fortitude and his courage to go down there and speak to the American people. I thought it was important to go down there and support that effort,” Cornyn, the No. 2 GOP leader, said in an interview Thursday.

Some Democrats were a little bewildered by what unfolded: a junior Republican senator taking a position on an antiterrorism program that was far to the left of most of their caucus, but creating such a stir that senior Republican senators felt compelled to go to the floor to defend him.

Sen. Martin Heinrich (D-N.M.), just two months into his tenure here, has the distinction of being the newcomer who has to sit in the chair presiding over debate late on Wednesdays — which meant he watched about three hours of Paul’s speeches up close while the chamber was mostly empty. “I was actually very engaged. It was fascinating to sit there and listen to him,” Heinrich said Thursday.

The Justice Department memo on Awlaki is believed to weigh factors such as the imminence of the threat he posed and the inability of U.S. forces to mount an operation to capture him.

In congressional testimony this week, Holder noted that the possibility of capturing terrorists is much greater in the United States and the use of deadly force is not permissible if capture is feasible, as in ordinary police operations. He also agreed that the United States does not have the constitutional power to kill terrorism suspects in the country who do not pose an imminent threat.

But Sen. Michael S. Lee (R-Utah) said that under his reading of a government white paper on targeting killing, the government’s definition of imminent threat appeared quite elastic.

“Imminence doesn’t need to involve anything imminent,” said Lee. “What does it mean if it doesn’t have to involve something immediate?

Holder said he had attempted to explain the government’s definition of imminent threat in a speech last March at Northwestern University.

He said that evaluation “incorporates considerations of the relevant window of opportunity to act, the possible harm that missing the window would cause to civilians, and the likelihood of heading off future disastrous attacks against the United States.” to denounce Paul’s quest

Paul Kane and Julie Tate contributed to this report.