That person is opposition leader Simon Bridges, a largely unknown figure in Australia, who took over the National party's reins after its shock 2017 election defeat.

To many outside New Zealand, it's scarcely thinkable that the compassionate and confident Ms Ardern might be turfed out of office in next year's poll.

Indeed, Kiwi political history doesn't support that notion either.

Quite apart from the recent rough and tumble in Canberra, it's been four decades since a freshly elected New Zealand Government wasn't given at least two terms in charge.

This month, among Labour's mishandling of sexual assault allegations within its ranks, cracks have appeared in Ms Ardern's authority.

And Mr Bridges is confident.

To those that know him, Mr Bridges has always been so.

"Half way through the rugby game ... this is anyone's to win," he told AAP this week in Wellington.

Mr Bridges was the youngest of six children, raised in unfashionable West Auckland by a Baptist minister father and schoolteacher mother.

He is the first leader of the National party in its 83-year-history to claim Maori heritage, through his father.

While his family background is decidedly un-National, his resume fits the establishment party to a tee.

He was head boy and a leader of the Young Nationals, a crown prosecutor at 24, then Oxford-educated and pre-selected for a safe seat by 31.

"I've always loved politics. Nobody else in my family have been involved in politics, but I could see it was important. It mattered," he said.

"It set my fire alight."

Finding his home on the conservative side of politics very early, Mr Bridges said the basis for joining National in his teenage years "sounds twee but it's because I aspire".

"And I want other people to aspire," he said.

Once in parliament, it didn't take long for prime minister John Key to notice Mr Bridges' talents.

He held several portfolios through the National's nine-year reign, including transport, energy and resources, communications, consumer affairs, and labour.

Perhaps the most significant position, though, was a weekly spot on the TVNZ couch on the top-rating Breakfast show.

Mr Bridges, then spiky-haired, was selected to spar each week with an emerging Labour star; none other than Ms Ardern.

And viewers loved it.

The pair sparkled in each other's presence, finishing the other's sentences, unable to conceal smirks while delivering their well-rehearsed political put-downs.

The chemistry led one producer to reveal that viewers would write in, asking if they were secretly in a relationship.

"It's fair to say Jacinda Ardern and I know every other well, not personally but professionally well," Mr Bridges says, now lacking any of his on-screen sparkle.

That's because it's not a personal rivalry Mr Bridges is keen to renew in next year's poll, given his opposite number's office and star power.

Indeed, Mr Bridges has toned down the more playful parts of his personality as leader, with one pundit describing him as "aggressively bland".

Having served for much of his political life under Mr Key, Mr Bridges seems to be cultivating a more managerial image; a safe pair of hands rather than a candidate New Zealanders will jump out of bed to vote for.

He hopes Kiwis will come to come to see Ms Ardern's government as insubstantial.

"I've never been a politician where it's about the personal or personalities," he said.

"It should be about policies and what you're going to deliver."

"The sad reality for Jacinda Ardern (is) her government is a mess.

"There's not a single part of its domestic agenda - and I use that word pretty loosely not to be snarky, but simply because it is hard to discern a strong one - that is doing well."

Mr Bridges' leadership hasn't been without missteps.

Earlier this year, the party trialled a "All sizzle, No sausage" attack ad, which was roasted as sexist.

In pursuit of the "average New Zealander" vote, he continues to attack Ms Ardern's pursuit of an international agreement to ban online extremist material, the Christchurch Call, labelling it a waste of time.

But after clocking up 18 months in the top job, Mr Bridges now looks assured of leading the National party to next year's poll against his old Breakfast TV sparring partner.

And he is confident that his party can win, ending Labour's Coalition with NZ First and the Green party after just one term.

"A lot of New Zealanders, especially those who voted for us, would say is we didn't lose (the last one)," he said.

"We were the most supported party with 44 per cent of the vote.

"New Zealanders are incredibly fair. Just as in Australia, we want to give folk a fair suck of the sav. They were open to this government impressing and doing the sort of things that need to be done.

"But the normal trajectory of a first-term government ... is that it galvanises support slowly and the opposition loses it. That certainly hasn't happened."

Australian Associated Press