Can Power reconcile her ardent human-rights interventionism with the “composite calculus” that must guide American policy? Photograph by Van Sarki

On July 17, 2013, the Senate Foreign Relations Committee met to consider the nomination of Samantha Power to be America’s Permanent Representative to the United Nations. She was an unusual choice. Although she had been a professor at Harvard’s Kennedy School of Government, and served on the National Security Council as the senior director for multilateral affairs and human rights, she had never been a diplomat. At forty-two, she would be the youngest-ever American Ambassador to the U.N.

Power was best known for her book “ ‘A Problem from Hell’: America and the Age of Genocide.” An indictment of what she called Washington’s “toleration of unspeakable atrocities, often committed in clear view,” it won the Pulitzer Prize in 2003. For her conviction that America has a responsibility to halt or prevent the suffering of civilians abroad, she had been caricatured as the Ivy League Joan of Arc. She had written (in this magazine and elsewhere) with unqualified assurance. As a speaker, “she was a performer of the first order,” Leslie H. Gelb, the former president of the Council on Foreign Relations, told me. “No notes, the fingers and the arms always flashing in the air, and a voice going from a whisper to a shout. She was pure theatre.”

In a 2002 interview on “Conversations with History,” a television series filmed in Berkeley, Power described a hypothetical need for a “mammoth protection force” to police a peace accord between the Israelis and the Palestinians. But after she began working as an adviser on Barack Obama’s Presidential campaign, in 2007, his critics quoted that interview in accusing him of harboring hostility toward Israel, and Power disavowed her comments. In a departure for a journalist, she quietly asked the host of the interview to remove the video from the Web, though portions of it still circulate online. To repair the damage, she subsequently approached Shmuley Boteach, a celebrity rabbi who ran for Congress in New Jersey, Abraham Foxman, of the Anti-Defamation League, and other prominent defenders of Israel, who endorsed her U.N. nomination. She knew that during her confirmation hearing her record, her vision of America’s role in the world, and her transformation from an activist to a political figure would receive intense scrutiny. Tom Nides, a former Deputy Secretary of State, told her that her chance of being confirmed was twenty per cent, at best.

When Power visited Senator Ted Cruz, the Texas Republican, he consulted a page of notes marked with a highlighter. She recalled, “Everything I’d ever written had just been pulled out and reduced, basically, to the things in my search that were the most cringe-worthy, things that you’d just say out of the corner of your mouth in a church basement somewhere, or whatever—they’re not your considered view.”

But Power’s ideas defy the usual partisan distinctions, and she cultivated some unlikely alliances on Capitol Hill. Senator Saxby Chambliss, a Republican from Georgia, where Power spent much of her childhood, shared her belief that, after President Bashar al-Assad of Syria deployed chemical weapons, Obama should have attacked the regime for crossing his “red line.” Chambliss told me, “We had some frank discussions about that. She said, ‘Hey, I’m working for the President—just remember that.’ And I said, ‘Yeah, I know, and here’s what I hope you’ll convey to the President.’ ” Chambliss added, “She has ideas that don’t always coincide with mine from a national-security perspective, but we’re pretty darn close.” He agreed to introduce her at her hearing. (She now sends him notes on his birthday.)

Power, who is five feet nine inches tall, with red hair that reaches the middle of her back, took her seat at the witness table, across from fourteen members of the committee. The gallery was full, and C-Span carried the event live. Power’s relatives and friends in the row behind her included her husband, the Harvard legal scholar Cass Sunstein, and their children: Declan, age four, and Rían, who was thirteen months. Power had resolved to treat the hearing as “you would run a corporation,” she told me; that is, know the objectives, liabilities, and “customer preferences.” The senators, she said, are “trying to get you to make news, potentially, or there can be efforts to create distance between you and the President.” She had to resist both ploys, while bearing in mind the senators’ consciousness of the cameras.

Marco Rubio, the Florida Republican, asked her to explain what she meant, in a 2003 essay in The New Republic, when she called for “a historical reckoning with crimes committed, sponsored or permitted by the United States.” Power disavowed the piece, saying that she “probably very much overstated the case,” and adding, “This country is the greatest country on earth. I would never apologize for America.” Rubio pressed the point, leaning toward the microphone, his eyes sweeping the gallery, and Power had to repeat the line—“This is the greatest country on earth”—two more times.

Ron Johnson, a Wisconsin Republican, brandished notes containing a quote in which Power referred to the United States as the “most important empire in the history of mankind.” He asked, “Do you believe America is an empire?”

Power gave a quick shake of her head and searched for the right words. “I believe that we are a great—a great and strong and powerful country, and the most powerful country in the history of the world,” she said. “Also, the most inspirational.” Empire, she went on, “is probably not a word choice that I would use today, having served.” She added, “Serving in the executive branch is very different than sounding off from an academic perch.”

Rand Paul, of Kentucky, who opposes many forms of American intervention, struck a sober note. He said he was concerned that sending American advisers into the war in Syria would lead to “more soldiers, and then we send platoons and regiments and generals.” He added, “So I would just say that even though noble intentions, I think, are yours, be very wary of what intervention means when we intervene. It’s one thing to send bread, but it’s another thing to send guns.”

Power responded, “Thank you, sir.”

To survive the questioning, Power had set aside the ferocity and independence that made her name. David Rieff, a frequent critic of Power’s humanitarian prescriptions, later derided her performance as that of an “apparatchik whose willingness to pander to her interrogators seemed to know no bounds.” When I asked Power about her performance, she smiled and said, “My thing in confirmation was, I can’t say anything that is not true.” If she received an awkward question, “I need to find something that is responsive, and that may just take it in a slightly different direction, but feels deeply true to me. That was what I felt I was able to do.” On August 1st, the Senate approved her nomination, by a vote of eighty-seven to ten.

In the acknowledgments of “The Audacity of Hope,” published while Obama was in the Senate, he wrote that Samantha Power “combed over each chapter as if it were hers.” At the time, she was a foreign-policy adviser in his office. Eight years later, many aides have left Obama’s Administration, but Power endures, in a role that is roughly equal parts envoy, protector, and, as she puts it, “pain in the ass.”