The Senate voted Thursday by a vote of 63 to 34 to confirm John Brennan, President Barack Obama’s nominee to head the Central Intelligence Agency after a filibuster sparked by the administration’s policy of targeted killings of terrorists.

On Wednesday, Sen. Rand Paul, R- Ky., staged a 12-hour filibuster to draw attention to his demand that Obama explicitly say whether he thinks he has the constitutional authority to order the killing of noncombatant American citizens on U.S. soil.

Related: McCain, Graham assail Rand Paul on drone policy

On Thursday Paul received a letter from Attorney General Eric Holder in which he said the president doesn’t have the authority "to use a weaponized drone to kill an American not engaged in combat on American soil."

Paul said on the Senate floor Thursday that he was “very pleased to have gotten this response back from the attorney general of the United States and I think Americans should see this battle we’ve had in the last 24 hours as something that’s good for the country.”

During his filibuster Paul mocked Brennan for saying at his confirmation hearing last month before the Senate Intelligence Committee, “What we need to do is optimize transparency on these (targeted killing) issues and at the same optimize secrecy and the protection of our national security.”

Brennan also said during his confirmation hearing that those who protest against the targeted killings “really have a misunderstanding of what we do as a government, and the care that we take, and the agony that we go through” to ensure that innocent bystanders aren’t hit in the drone strikes in Yemen and other countries. “The American people would be quite pleased to know that we’ve been very disciplined and very judicious,” he argued.

One Democrat who voted against confirming Brennan, Judiciary Committee chairman Sen. Patrick Leahy of Vermont said he'd reluctantly opposed the nomination because "the administration has stonewalled me and the Judiciary Committee for too long on a reasonable request to review the legal justification for the use of drones in the targeted killing of American citizens."

The administration, Leahy said, "made the relevant OLC (Office of Legal Counsel) memorandum available to the Senate Select Committee on Intelligence in order to advance this nomination.  I expect the Judiciary Committee, which has oversight of the Office of Legal Counsel, to be afforded the same access."

Thirteen Republican senators voted for Brennan, while two Democrats and independent Sen. Bernie Sanders of Vermont, who caucuses with the Democrats, voted against him.

In making the case for Brennan, Intelligence Committee Chairman Sen. Dianne Feinstein, D- Calif. said that his 25 years as a CIA analyst, head of counterterrorism efforts and White House homeland security advisor make him the best person for the job. “No one is better prepared to be CIA director than Mr. Brennan,” she said.

In opposing Brennan, Intelligence Committee ranking Republican member Sen. Saxby Chambliss of Georgia criticized Brennan’s answers about leaks from the Obama administration on terrorist operations.

Implying that Brennan himself was a leaker, Chambliss said he wondered about the credibility of Brennan’s explanation of his role in funneling information to four news media commentators about a foiled 2011 al Qaida in the Arabian Peninsula (AQAP) bombing plot.

Chambliss also said Brennan was an architect of the administration’s policy of refusing to send any more new terrorist suspects to Guantanamo Bay.  The Obama administration, he said, “appears to be avoiding opportunities to capture terrorists in favor of just killing them, or relying on our foreign partners to do our intelligence collection for us.”

After holding forth on the Senate floor for almost 13 hours, Kentucky Republican Sen. Rand Paul has ended a lengthy filibuster of the president's nominee to lead the CIA. 

Paul, who cited objections over the administration's policy regarding potential drone attacks on U.S. citizens, relinquished the Senate floor at nearly 1 a.m. ET early Thursday morning. 

In the end, it was nature that called. 

"I've discovered that there are some limits to filibustering, and I am going to have to take care of one of those in a few minutes here," he said to laughter after thanking his supporters and staff. 

Forcing the question of civil liberties and U.S. drone policy into the spotlight, what began as a one-man stand increasingly gained steam - and supporters - both in the Senate chamber and in social media throughout the day. 

Paul's traditional or "talking" filibuster -- dependent on one senator's control of the floor rather than a tally of votes -- continued into the wee hours as the Kentucky lawmaker pressed his case against the administration's policy on drone strikes on American soil.

It was the first use of the tactic since 2010, when Independent Sen. Bernie Sanders of Vermont held the Senate floor for eight hours and 37 minutes - a length Paul surpassed. 

The senator was joined on the floor throughout the day and night by other lawmakers, who stepped in to help continue the filibuster by asking lengthy questions on the Senate floor. His colleagues' contributions also included statements of support, the reading of tweets supporting Paul's efforts and the quoting of rap lyrics, Shakespearean prose and classic Hollywood films.

In a sign that Paul's cause had moved beyond just the most conservative wing of the party, Senate Minority Leader Mitch McConnell - Paul's fellow Kentuckian who is facing re-election in 2014 - joined close to midnight to offer support for Paul's "tenacity and conviction" and to announce that he will oppose CIA nominee John Brennan's confirmation. 

Republican Sens. Mike Lee of Utah, Ted Cruz and John Cornyn of Texas, Jerry Moran of Kansas, Saxby Chambliss of Georgia, Pat Toomey of Pennsylvania, Marco Rubio of Florida, Jeff Flake of Arizona, Ron Johnson of Wisconsin, Tim Scott of South Carolina, John Thune of South Dakota and John Barrasso of Wyoming -- as well as Democrat Ron Wyden of Oregon -- also participated. 

The filibuster continued late into the night despite earlier Democratic attempts to defuse it. 

First, Paul rebuffed Majority Leader Harry Reid's attempts to move to a vote on the nomination, pushing the final vote at least until Thursday. 

Hours later, Democratic Whip Dick Durbin of Illinois objected to Paul's request that the Senate take up a non-binding sense of the Senate resolution stating that the U.S. government cannot target "noncombatants" with drones on American soil. 

Arguing that such a resolution would be premature, Durbin instead invited Paul to testify at an upcoming hearing on the issue of drones. 

But that offer was not enough for Paul to halt his protest. 

Paul objects to what he calls the Obama administration's lack of clarity over whether a suspected terrorist who is an American citizen can be targeted with a drone strike within U.S. borders. 

In a response to a letter of inquiry, Attorney General Eric Holder wrote to Paul this week that such a targeted strike is "possible, I suppose" in a catastrophic circumstance, although the administration has "no intention" of doing so.

Paul began his filibuster as Holder testified before the Senate Judiciary Committee, where the attorney general reiterated some of that defense of the administration's policy. 

Hours into his filibuster, Paul acknowledged that Brennan is still likely to be confirmed, saying the lengthy delay is merely a "blip" in his nomination. But he and other participants emphasized that the debate is intended to shine a spotlight on the government's balance of civil liberties with national security. 

Over six hours after beginning the filibuster, a visibly tired Paul could be seen eating what appeared to be several pieces of candy in between sentences. At one point, Sen. Mark Kirk, R-Ill., set a thermos and an apple on his desk. 

"You must surely be making Jimmy Stewart smile," Cruz said of Paul upon taking the floor, alluding to the famous filibuster portrayed by the actor in the 1939 film "Mr. Smith Goes to Washington."

NBC's Mike Viqueira and Frank Thorp contributed to this report. 

This story was originally published on Wed Mar 6, 2013 12:34 PM EST

The Senate Intelligence Committee voted on Tuesday in favor of John O. Brennan's nomination to become the next director of the CIA, clearing the way for his confirmation before the whole Senate.

The intelligence panel voted 12-3 in a closed-door session to favorably report Brennan, the Homeland Security adviser to President Barack Obama. Tuesday's vote could clear the way for Brennan's confirmation as soon as this week.

The three senators voting against Brennan's nomination in committee, all Republicans, were Sens. Jim Risch (Idaho), Saxby Chambliss (Ga.) and Tom Coburn (Okla.). Chambliss is the committee vice chairman and said he would be explaining his "no" vote on the Senate floor in the coming days.

Brennan faces some measure of rare, bipartisan resistance from Republicans who wish for more information from Obama about the Sept. 11, 2012 attacks in Benghazi and liberals who want more details about Brennan's role in advising covert drone strikes against terrorist targets.

If any of those senators object to moving forward with Brennan's nomination before the whole Senate, it would trigger the same 60-vote threshold -- a de-facto filibuster -- to which now-Defense Secretary Chuck Hagel's nomination was subjected.

This story was originally published on Tue Mar 5, 2013 3:40 PM EST

Updated at 6:26 p.m. ET: At his confirmation hearing Thursday before the Senate Intelligence Committee John Brennan, President Barack Obama’s nominee to head the Central Intelligence Agency, defended Obama’s policy of targeted killings of terrorists, saying that some Americans had a misimpression that “we take strikes to punish terrorists for past transgressions. Nothing could be further from the truth. We only take such action as a last resort to save lives when there’s no other alternative” to avert a threat to the nation.

Despite the questions about Obama’s use of targeted strikes to kill people whom the administration calls “senior operational leaders” of al-Qaida or affiliated groups, it seemed by the end of the three-and-a-half hour hearing that Brennan was certain to be confirmed. Intelligence Committee Chairman Sen. Dianne Feinstein, D-Calif., called him “a fine and strong leader” and pledged her support for him. 

Alluding to some raucous protesters who had interrupted and delayed the hearing, Brennan said, “They really have a misunderstanding of what we do as a government, and the care that we take, and the agony that we go through” to ensure that innocent bystanders or civilians aren’t hit in targeted killings. “People are reacting to a lot of falsehoods that are out there.”

Related: GOP senators assail Gen. Dempsey and Obama for response to Benghazi attack

He said, “I think the American people would be quite pleased to know that we’ve been very disciplined and very judicious” and that the Obama administration only uses targeted killings “as a last resort.”

On American citizens who become involved in al-Qaida or allied group abroad, Brennan said, “any American who joins al-Qaida will know full well that they have joined an organization that is at war with the United States” and that the U.S. government “will do everything possible to destroy that enemy to save America lives.” When Sen. Ron Wyden, D-Ore., asked if such a person could surrender before the U.S. government killed them, Brennan said “they have the ability to surrender anytime, anywhere.”

Brennan told Wyden if a person is killed by mistake in a targeted killing, the government should acknowledge it publicly.

In answering another question from Wyden about the public’s understanding of the standards Obama uses to determine if he has enough evidence to order the killing of an American who is involved in al-Qaida terrorist plans, Brennan said, “What we need to do is optimize transparency on these issues and at the same optimize secrecy and the protection of our national security. I don’t think it’s one or the other.” He said, “We need to explain to the American people what are the thresholds for action” and what procedures the CIA and the president use to ensure that the killing are legal.

Thursday’s hearing was a chance for senators on the panel to ask Brennan whether Obama is using drone strikes as a less politically troublesome option than capturing detainees and putting them in Guantanamo.

“I never believe it is better to kill a terrorist than to detain him,” Brennan told Intelligence Committee ranking Republican member Sen. Saxby Chambliss, R-Ga. “We want to detain as many terrorists as possible so we can elicit the intelligence from them in the appropriate manner so that we can disrupt follow-on terrorist attacks.”

But Brennan did not reveal how many high-value al-Qaida suspects had been arrested and interrogated since Obama became president, promising Chambliss only that he’d get that information for him.

In reply, Chambliss said during Obama’s presidency that only one high-value al-Qaida suspect has been arrested and interrogated.

On the targeted killings policy, Obama directed the Department of Justice Wednesday to give the congressional intelligence committees "access to classified Office of Legal Counsel advice” related to the policy. This move came after NBC News on Monday published a Justice Department white paper giving the legal basis for the targeted killings.

Win Mcnamee / Getty Images

John Brennan, nominated by U.S. President Barack Obama to be the next Director of the Central Intelligence Agency, testifies before the Senate Intelligence Committee February 7, 2013 in Washington, DC.

The memo said it was lawful for the president to order people who are leaders of al-Qaida or “an associated force” killed when such people pose an imminent threat of attack against the United States and when it isn’t feasible to capture them. This is true even if they happen to be American citizens.

Brennan and other Obama administration officials say that the congressional authorization to use military force enacted after the Sept 11. 2001 attacks provide all the legal authority Obama needs to order the killing of al Qaida terrorists or those plotting attacks on the United States.

Feinstein complained to Brennan that the Justice Department has still not turned over eight Office of Legal Counsel opinions giving legal rationale for the killings. And she complained that only senators on the panel and not their staff members are allowed to read them. “The Justice Department is not yet followed through on the president’s commitment,” added Wyden.
In the opening stage of the hearing senators wanted to ask Brennan, who worked at the CIA for 25 years, about his knowledge of the enhanced interrogation techniques including waterboarding that were used by CIA operatives prior to 2008 to get information from al Qaida detainees.

“I did not take steps to stop the CIA’s use of those techniques. I was not in chain of command of that program,” Brennan told Chambliss.

“I was aware of the program – I was CC’d on some of those documents -- but I had no oversight,” he added. He also said, “I had expressed my personal objections and views to some agency colleagues” about some of the EIT methods such as waterboarding.

Brennan told Chambliss that he had the impression in 2007 that "there was valuable information coming out" from Enhanced Interrogation Techniques, but that after having read parts of a 6,000-page internal CIA review of the EIT program, he now doesn’t know if those techniques did elicit valuable information.

Saul Loeb / AFP - Getty Images

CIA director nominee John Brennan during a meeting on Capitol Hill in Washington on Jan. 31, 2013.

Amid new developments and revelations, President Barack Obama’s national security policies, past and future, are set to come under Senate scrutiny Thursday.

Most notably, Obama’s nominee to head the Central Intelligence Agency, John Brennan, will address what role the targeted killings of terrorists, either by using drone strikes or other means, have played and should play in national security policy.

Questions about targeted killings intensified Monday after a report by NBC News revealed a Justice Department memo which argued it was lawful for the president to target U.S. citizens who are leaders of al-Qaida or “an associated force.” Brennan will be appearing before the Senate Intelligence Committee for his confirmation hearing.

On Wednesday, an Obama administration official said the president had directed the Justice Department to give the congressional intelligence committees access to classified memos justifying the targeted killings policy. Until now the administration had refused to do this.  

Addressing the past on Thursday will be Defense Secretary Leon Panetta and Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, as they testify before the Armed Services Committee about the Sept. 11, 2012 attack on the U.S. diplomatic mission in Benghazi.

Senators on the panel -- especially Sen. Lindsey Graham, R-S.C. -- want to know how the U.S. military reacted to the attack, and what the Defense Department’s internal review revealed after the event.

The two hearings will feature contrasting political color: Republicans -- led by Graham, Sen. John McCain of Arizona and Sen. Kelly Ayotte of New Hampshire -- have been the ones who have made an issue of the Benghazi attack almost since it took place. They’ve implied that a full accounting of what happened was delayed until after the presidential election. Graham held up Obama’s nomination of Chuck Hagel to be defense secretary until he could get a chance to question Panetta about Benghazi.

But Obama’s drone policy -- directed largely by Brennan in his role as Obama’s counter-terrorism adviser -- has drawn criticism both from progressives on the left and those on the right who are fearful of an excessive concentration of power in the presidency.

On Benghazi, much is already known. In its report on the attack, the Senate Homeland Security and Governmental Affairs Committee said last December that Panetta’s Defense Department and Hillary Clinton’s State Department hadn't jointly studied the availability of U.S. military forces to defend or rescue the U.S. diplomats in Benghazi in the event of a crisis.

The Pentagon’s Africa Command didn’t have planes, helicopters, or other forces close to Benghazi on the day of the attack. “The Djibouti base was several thousand miles away. There was no Marine expeditionary unit, carrier group or a smaller group of U.S. ships closely located in the Mediterranean Sea that could have provided aerial or ground support or helped evacuate personnel from Benghazi,” the report said.

As for Brennan and drones, Micah Zenko, a fellow at the Council on Foreign Relations and author of a new report called “Reforming U.S. Drone Strike Policies,” said Obama’s choice of him as CIA director “now places him as the lead executive authority over all CIA drone strikes. The real question is whether John Brennan’s move from the White House to Langley to be director of the CIA is in fact an effort for the CIA to get out of the drone strikes business.”

Zenko noted that Panetta recently said that the Pentagon, not the CIA, should be conducting the drone strikes against al-Qaida suspects.

But Zenko cautioned against those who would head into the Brennan hearing with high hopes for new information. Having read transcripts of the past 10 CIA director confirmation hearings, he said, “It would be unprecedented if there were an in-depth discussion about ongoing covert activities.” The Senate Intelligence Committee “simply doesn't work that way, especially under chairman Sen. (Dianne) Feinstein” of California, he said.

Zenko added that the most useful line of questioning of Brenna would be regarding his conceptions of airpower. Brennan has repeatedly used the cancer analogy for air strikes killing terrorists without damaging the surrounding “tissue.”

“That's a dangerous, antiseptic, and unrealistic conception of military force,” Zenko said.

Interrogation vs. deadly strikes
But Obama spokesman Jay Carney told reporters at a White House briefing Wednesday, “Far fewer civilians lose their lives in an effort to go after senior leadership in al-Qaida” by using drone attacks “as opposed to an effort to invade a country with hundreds and thousands of troops and take cities and towns.” Implication: if you want to avoid another Iraq or Afghanistan, then support Obama’s drone policy.

Carney said Obama believes “that we need to move forward with more transparency as well as create, in his words, a legal framework around how these decisions are made.” But Obama believes he has the full constitutional authority to order targeted killings -- “transparency” or no transparency.

For those skeptical of Obama’s policy, there will be two other possible lines of questioning directed at Brennan:

1. Do the foreign policy costs of Obama’s use of drones -- alienating and angering people in Muslim countries -- outweigh its benefits?
2. Does the drone policy suggest that Obama would rather kill jihadists than capture them? Adding more detainees to those already held at Guantanamo -- a facility he pledged to close but hasn’t -- could amount to a political public relations headache.

The drone strikes have been unpopular in Pakistan and other countries. Making the case that drone strikes have high costs as well as benefits, the former U.S. commander in Afghanistan, Gen. Stanley McChrystal, told Reuters recently, “What scares me about drone strikes is how they are perceived around the world. The resentment created by American use of unmanned strikes … is much greater than the average American appreciates.”

Brennan has an opportunity on Thursday to rebut this view. He argued last August that “contrary to conventional wisdom, we see little evidence that these actions (drone strikes) are generating widespread anti-American sentiment or recruits” for al-Qaida. The targeted strikes against terrorists, he said, “are not the problem, they are part of the solution.”

Finally, Thursday’s Brennan hearing is a chance for senators on the panel to ask him whether Obama is using drone strikes as a less politically troublesome option than capturing detainees and putting them in Guantanamo.

This is an argument that former Bush administration officials such as ex-CIA director Gen. Michael Hayden and former CIA legal counsel John Rizzo have made.

Last week in a panel discussion at the American Enterprise Institute, a conservative Washington think tank, Hayden said interrogating al-Qaida operatives is a vital source of insight into the terrorists’ plans and capabilities:

But he warned, “We have made it so legally difficult and so politically dangerous to capture that it seems, from the outside looking in, that the default option is to take the terrorists off the battlefield in another sort of way” – in other words, by killing them. This could result in a loss of valuable intelligence.

Rizzo said, “It’s always been in the agency’s institutional DNA to want to collect intelligence by all sorts of means, especially human intelligence. You can’t collect human intelligence from a dead guy.”

Related:

White House: Congress to get classified drone info

4 key questions about controversial Justice Department drone memo

Legal experts fear implications of White House drone memo

Jewel Samad / AFP - Getty Images, file

White House counterterrorism adviser John Brennan's career includes a stint as CIA station chief in Saudi Arabia.

WASHINGTON -- Counterterrorism adviser John Brennan will be nominated as director of the Central Intelligence Agency by President Barack Obama, White House officials told NBC News on Monday.

Brennan worked at the CIA for 25 years, including a stint as station chief in Saudi Arabia. He also served as chief of staff to then CIA Director George Tenet from 1999 to 2001, when he was named the agency's deputy executive director. 

Obama was expected to make the announcement on Monday.

Full coverage from NBC Politics

As Brennan has been involved in major national security issues since 9/11, he should be able "to hit the ground running" at the CIA, one official told NBC News.

If confirmed, Brennan will succeed retired general David Petraeus, who resigned amid a scandal over an extramarital affair with his biographer.

On Sunday, an official told NBC News that Obama planned to nominate former Sen. Chuck Hagel to be secretary of defense.

Hagel is a moderate Republican and decorated Vietnam combat veteran who is likely to support a more rapid withdrawal of U.S. troops from Afghanistan. If confirmed, Hagel would give Obama a whiff of bipartisanship in his Cabinet. 

Senators signal tough fight for Hagel

The Hagel announcement was also scheduled for Monday.

Obama nominated Sen. John Kerry, D-Mass., as his next secretary of state in December, his first step in filling out his second term Cabinet and national security team.

NBC News' Peter Alexander and Reuters contributed to this report.