Among the low points of the Obama administration’s final weeks was its refusal to veto a blatantly anti-Israel resolution in the UN Security Council.

When Nikki Haley attended her first Security Council session a few weeks later as the new ambassador under President Trump, she promptly reversed course. “I am here to emphasize," she told reporters, "that the United States is determined to stand up to the UN’s anti-Israel bias.”

Haley lived up to that promise on Tuesday, when she vetoed a resolution demanding that the Trump administration rescind its decision recognizing Jerusalem as Israel’s capital. She followed up her veto with formal remarks calling the resolution “an embarrassment” to the UN and scolding those who “presume to tell America where to put our embassy.” On Twitter the next day, Haley laid down a marker ahead of Thursday’s vote on the topic in the UN General Assembly.

“When we make a decision … abt where to locate OUR embassy, we don’t expect those we’ve helped to target us," she tweeted. "On Thurs there’ll be a vote criticizing our choice. The US will be taking names.”

Reckless and counterproductive? Hardly. Haley’s performance at the UN has been a joy to behold. The former South Carolina governor, who came to the job with no foreign policy experience, has turned out to be a natural — behind the scenes no less than in the spotlight.

This fall, Haley succeeded in winning unanimous Security Council approval for economic sanctions on North Korea in response to its continuing nuclear belligerence. Displaying a knack for political deal-making, she initially proposed a package of sanctions so severe that Russia and China would doubtless have vetoed them had they been put to a vote. Then she set out to negotiate a compromise — dropping demands for a total oil embargo, for example, but digging in on other restrictions. “That made it possible for both China and Russia to join the consensus," reported The Nation, a journal far from friendly to the Trump administration. "Haley got a unanimous 15-0 ‘yes’ vote against North Korea, an outcome that sent a message of unity” to Pyongyang.

Last week she did it again, winning unanimous Security Council approval for a new layer of sanctions on North Korea.

Nearly a year into the job, America’s ambassador to the UN comes across as refreshing, unabashed, principled, and savvy. She is one of the most popular officials in a historically unpopular administration. “The breakout star of Trump’s Cabinet," CNN calls her.

This would be impressive under any circumstance. It’s especially so in the Trump presidency, which has been very rough on the reputations and careers of numerous high-level officials. It’s even more remarkable given Haley’s own history with Trump. She publicly opposed his presidential bid, urged Republicans not to "follow the siren call of the angriest voices,” and endorsed Marco Rubio in the South Carolina primary. After Trump won that primary, he lashed out on Twitter: “The people of South Carolina are embarrassed by Nikki Haley!” (Her unruffled response: “Bless your heart.”)

Trump holds grudges, yet he made Haley a key diplomatic face of his administration. Trump hates to share the spotlight, but he has done nothing to impede Haley’s celebrity. And while the president has publicly rebuked or undercut other Cabinet members, including Secretary of State Rex Tillerson, he hasn’t done so to Haley — not even when she has expressed views and taken stands that are quite different from his.

Which she has. Haley has loudly denounced Russia’s continuing aggression in Ukraine, vowing that sanctions would never be lifted until Crimea is restored to Ukrainian control. Despite Trump’s open embrace of Vladimir Putin, Haley warns bluntly: “We cannot trust Russia. We should never trust Russia.”

Haley vigorously castigates dictatorships for their human rights abuses, something that neither Trump nor Tillerson considers a priority. “For me," Haley stresses, "human rights are at the heart of the mission of the United Nations.”

On most issues, of course, Haley supports the president, as all ambassadors do. “I don’t go rogue on the President,” she has said. But she has figured out how to distance herself from Trump even when defending him. During the furor over banning travelers from several Muslim nations, Haley publicly justified it as a security measure. But she immediately and more memorably added that it would be “un-American” to “ever ban anyone based on their religion.”

Haley plainly outshines Tillerson, a hapless if well-meaning secretary of state who has managed to wow neither the president nor the public. Tillerson brought an admirable international business resume to the job, but he lacks the political skills that Haley acquired during her meteoric rise from total unknown — she was the bookkeeper for her mother’s clothing business — to governor of South Carolina. Haley has quickly acquired the foreign-policy fluency in which she was totally deficient a year ago. It is quite plausible that Trump will ask her at some point to replace Tillerson at the State Department.

Critics treated Haley’s warning that the US would be “taking names” on the UN’s Jerusalem resolution as an appalling diplomatic gaffe. It wasn’t. The best UN ambassadors have always known that the job entails more than behind-the-scenes wheeling and dealing: It calls for the vigorous defense of moral truth as well. Like Adlai Stevenson, Daniel Patrick Moynihan, and Jeane Kirkpatrick, Haley has shown that she can be effective in the UN while bluntly decrying the lies and prejudices that sully it. Her first year on the job has been brilliant. Whatever Trump may have gotten wrong, his choice of Nikki Haley was a masterstroke.

Jeff Jacoby is a columnist for The Boston Globe.