Premiers, prime ministers, presidents and potentates rarely go of their own volition - it being in their nature to cling to power.

Self-confidence that would be thought narcissistic in other walks of life, are more-or-less normal among political leaders.

While few are as unvarnished as Donald Trump, vanity is hard-wired into the system, as is the gall to seamlessly conflate one's personal advancement with the national interest.

But Jacinda Ardern turned that on its head.

Not only has the world-famous prime minister of an often overlooked nation chosen to leave while on top, but her voluntary departure underscores how she rewrote the male-centric rules of power to stress service, empathy, kindness, and authenticity.

These were the qualities Treasurer Jim Chalmers listed off in his public remarks on behalf of Australia.

Lauding the 42-year-old Ardern as "not a garden variety prime minister" and as "a source of remarkable inspiration around the world" Chalmers said she had these virtues in "the best imaginable combination".

Ardern's response to the Christchurch mosque shootings in 2019 was a case in point. Her reflexive compassion provided comfort to the bereaved but crucially set a tone of unity at a moment of unfathomable division.

It was New Zealand leadership, 100 per cent pure.

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Kiwis will go to the polls in October with no certainty that the Labour government Ardern leads will be returned.

Inevitably, this will colour some of the analysis of her seismic resignation - the suggestion being that she was abandoning ship.

But this is probably old thinking of the kind Ardern's 21^st century approach had already rendered haggard and disingenuous.

Given the way she conducted herself in office, the outgoing PM might be entitled to a greater than usual presumption of authenticity.

As she noted, she would have been seeking not just another year in office but another term.

Describing national leadership as "the most privileged job anyone could have", it took emotional maturity to conclude she "no longer had enough in the tank to do it justice".

In many ways, New Zealand has been ahead of Australia, not least because Ardern is that country's third female leader.

She was also the first leader of any modern democracy to carry a child and give birth while in office. "I'm just pregnant, not incapacitated," she quipped in 2018 amid altogether too much fuss.

As a tremulous Joe Biden shuffles his way to a second embarrassing term, Ardern's resignation, exhibits another virtue rare in male politics - a sense of one's own dispensability.

That's another conundrum: a leader balanced enough to relinquish power may be just the kind of person we need to stay on.