A couple of months ago, New Zealand prime minister Jacinda Ardern hobnobbed among the billionaires and global cognoscenti gathered at the World Economic Forum in Davos, Switzerland. She extolled the fight against climate change alongside Prince William and championed her government's plans to prioritise the societal – not just economic –“well-being” of her country.

In a polite rebuke of Donald Trump and other right-wing politicians, Ms Ardern said she hoped world leaders would recognise the virtue of “more compassionate” domestic policies that would obviate “the false promise of protectionism and isolation”. Then she partied with Google.

Ms Ardern, whose personal magnetism drove her Labour Party to electoral victory in 2017, has appeared in a Vogue photo spread and on American late-night television. When she gave birth to a baby in office – and then brought her 3-month-old daughter to the United Nations General Assembly last year – the unusual precedent only burnished her image as a global feminist icon. There even was a term for her celebrity: “Jacindamania”.

But not all at Davos were impressed with the charismatic, liberal and young – Ms Adern is just 38 – world leader.

Speaking on the condition of anonymity to the Washington Post's WorldView, one Western fund manager with dealings in the Asia-Pacific region scoffed that Ms Ardern “was just a less annoying Justin Trudeau with an easier country to run” – a jab both at her and the Canadian prime minister, another darling of the centre left who critics argue has traded too long on his rosy image rather than actual policy achievements.

New Zealand shootings: Victims of Christchurch mosque terror attacks Show all 11 1 /11 New Zealand shootings: Victims of Christchurch mosque terror attacks New Zealand shootings: Victims of Christchurch mosque terror attacks Zakaria Bhuiyan People gather hoping to find out information about Zakaria Bhuiyan who is still missing after the mosques shootings in Christchurch. David Moir/AFP New Zealand shootings: Victims of Christchurch mosque terror attacks Mucad Ibrahim Three-year-old Mucad Ibrahim, the youngest known victim of the mass shooting at two mosques in Christchurch, New Zealand, on 15 March 2019. Abdi Ibrahim via AP New Zealand shootings: Victims of Christchurch mosque terror attacks Nadeem Rasheed Nadeem Rasheed, brother of Pakistani Naeem Rashid who died alongside his son Talha Naeem, 21, who were killed in shooting at a Mosque in Christchurch, at their home town in Abbottabad, EPA New Zealand shootings: Victims of Christchurch mosque terror attacks Omar Nabi Omar Nabi speaks to the media about losing his father Haji Daoud Nabi, 71, in the mosque attack REUTERS New Zealand shootings: Victims of Christchurch mosque terror attacks Ash Mohammed Ash Mohammed, right, talks to a police officer about his father and two brothers who are missing near the Masjid Al Noor mosque AP New Zealand shootings: Victims of Christchurch mosque terror attacks Akhtar Khokhur Akhtar Khokhur, 58, shows a picture of her missing husband Mehaboobbhai Khokhar, 65. AP New Zealand shootings: Victims of Christchurch mosque terror attacks Wasseim Alsati A note is seen on a window of a door at the family home of Wasseim Alsati in Christchurch on 17 March 2019. AFP/Getty Images New Zealand shootings: Victims of Christchurch mosque terror attacks Haroon Mahmood Relatives offer condolences to nephew (centre) of Haroon Mahmood, a Pakistani citizen who was killed in Christchurch mosque shootings. AP New Zealand shootings: Victims of Christchurch mosque terror attacks Farid Ahmed Farid Ahmed (pictured) survived the Al Noor mosque shootings but his wife Husne was killed. AFP/Getty Images New Zealand shootings: Victims of Christchurch mosque terror attacks Syed Areeb Ahmed A relative shows a picture of Syed Areeb Ahmed, a Pakistani citizen who was killed the Christchurch mosque shooting. AP New Zealand shootings: Victims of Christchurch mosque terror attacks Naeem Rashid A relative looks at a picture on a mobile phone of Pakistani nationals Naeem Rashid and his son Talha Naeem (right) who died in the Christchurch shootings. AFP/Getty Images

As Washington Post journalist Anna Fifield wrote on Monday, Ms Ardern has “had plenty of political trials and tribulations”.

Ms Fifield explained: “Her handling of the economy has been criticised, and her efforts to introduce more affordable housing have been plagued by embarrassing bureaucratic blunders. Detractors said she was all style and no substance.”

And, then, the terrorist attack in Christchurch happened. Since a self-proclaimed white supremacist burst into two mosques in the South Island city on Friday, killing at least 50 people and wounding dozens more, Ms Ardern has become the face of her nation's sorrow and grief, and its resolve.

Observers hailed the calm and compassion she has shown in the wake of the worst mass killing in her country's modern history. She led a multiparty delegation from the country's capital, Wellington, to Christchurch, donning a black headscarf and mourning with relatives and friends of the victims.

She also promised to cover the funeral costs of all those slain. A photographer who covered her visit marvelled at the prime minister's composure and empathy.

“Ardern's performance has been extraordinary – and I believe she will be strongly lauded for it both domestically and internationally,” political commentator Bryce Edwards of Victoria University in Wellington told Reuters.

Ms Ardern has also followed through in rhetoric and action. She immediately decried the white-nationalist ideology that fuelled the massacre and spoke firmly for what she believed were her country's values. The death toll itself was a catalogue of New Zealand's budding diversity.

“Among the dead were worshipers from Pakistan, India, Bangladesh, Turkey, Malaysia, Indonesia, Somalia and Afghanistan,” Washington Post journalists noted. “The youngest was a 3-year-old boy born in New Zealand to refugee parents from Somalia.”

“We represent diversity, kindness, compassion,” Ms Ardern said on Friday. “A home for those who share our values. Refuge for those who need it. And those values will not and cannot be shaken by this attack.”

She insisted that the victims “are us” and the “perpetrator is not”. Addressing the suspected shooter, an Australian national now in police custody, she warned: “You may have chosen us – we utterly reject and condemn you.”

Now, Ms Ardern says she will pursue changing New Zealand's gun laws. She said that her government will announce plans “within 10 days of this horrific act of terrorism” that she believes will make “our community safer.”

My colleagues reported that the “measures could include restricting the military-style semiautomatic weapons that were used in the attacks.” Ms Ardern has discussed full bans on these semiautomatic weapons as well as potentially requiring licenses for individual guns.

American advocates for gun control can only look on wistfully at the pace with which Ms Ardern can act. Both the United States and New Zealand “are among the only nations without universal gun registration rules, and both have strong gun lobbies that have stalled previous attempts to rein in gun owners' liberties,” noted Washington Post journalist Rick Noack.

But he added that Ms Ardern has less to fear politically in her country than a liberal American leader, who would have to contend with the outsize influence of the National Rifle Association and a political system that gives disproportionate weight to rural, conservative parts of the country.

For good measure, Ms Ardern also gently spoke out against Trump, rejecting his attempts to play down the rising threat of white-supremacist terrorism and urging him to show his solidarity with “all Muslim communities”. Such a message of support has yet to come from the White House.

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With her reputation burnished in the aftermath of national tragedy, Ardern finds herself in a situation similar to that of former Norwegian prime minister (and now NATO secretary general) Jens Stoltenberg, who won plaudits for his compassion and poise after another white-nationalist terrorist, Anders Breivik, murdered 77 people in 2011. In a speech, he famously vowed to combat “hatred with love.” But Stoltenberg's aura soon faded, especially after a 2012 inquiry found that his government could have thwarted the attack. He was voted out of office in 2013.

For now, Ms Arden's political prospects are more robust. While Mr Trump goes on a weekly Twitter meltdown and Theresa May fumbles over Brexit, Ms Ardern's decisiveness and conviction have laid down a marker.

“Was there any substance to her? That question is asked of all women leaders,” wrote Guardian columnist Suzanne Moore. “What is underneath? Where is the steel? Now, in the most horrific of circumstances, we have seen the steel.”