The key message she will deliver to voters will be the dangers of change: a change in Government.
Is the change she spoke of in 2017 still on her agenda, or has Covid-19 made change unaffordable?
The Herald sat down with Ardern in her ninth-floor office of the Beehive just before she left to campaign to regain the right to hold that office.
ON the bookshelf behind Ardern is a book titled "Women Who Win: or making things happen." It is William M Thayer's 1897 book of biographies about women: Florence Nightingale, Harriet Beecher Stowe, Elizabeth Fry, Mary Lyon.
This election is a battle of two women, Ardern and National Party leader Judith Collins.
Only one can win and the one sitting in front of the bookshelf has a distinct advantage.
Things are very different from just six months earlier when polls had Labour and National neck and neck.
National's attacks on Labour's failure to deliver on key policies such as KiwiBuild and light rail were having some effect.
Then along came Covid-19. Now, as the campaign proper begins, Labour is sky high in the polls, while National is on to its third leader in three months.
It is little wonder Ardern's campaign will focus almost relentlessly on the Covid-19 response rather than risk putting up potentially unpopular policies that could let National back into the race.
Ardern says Labour's campaign is by necessity very different to what was planned six months ago.
"The pledges we make will be different; a lot of our plan we have rolled out in the last three months because that's when it's been needed.
"Banking it up just for the purposes of a political campaign, I don't think that would have been the right thing to do."
Ardern says her key campaign message will be that changing the Government during the Covid-19 recovery will "slow things down".
Collins has compared the contest between the two of them as between "someone who knows how to lead" and someone who "basically just communicates really well".
Asked about Collins, Ardern says "I don't really know Judith Collins particularly well, so I find it hard to pass judgment or comment.
"But what I do know is New Zealanders know me; I've been in this role now for two years and 10 months. They've seen how I lead when the unexpected arises.
"So I think they have a good measure of who I am as a leader, and I hope they can make a judgment based on that."
The barb in that is that if Ardern does not know Collins well enough to judge her, then Collins does not know Ardern well enough.
One of Ardern's new campaign lines is "we cannot afford to put on the brakes". Asked what that means exactly, she says "changing leadership".
"We have a plan, and if people decide they want to opt for a different plan, that obviously slows things down. Changes of government slow things down.
"Our view is we already have our Covid recovery and rebuild plan under way and that's what we'll be presenting to the public, alongside some of our other policies.
"But this will predominantly be a Covid election."
One other thing could put on the brakes: another outbreak of Covid-19.
Ardern says if community transmission of Covid-19 returns, her campaign will grind to a screaming halt.
If needed, she would not hesitate to put the country back into lockdown. "If that is what is needed, that is what is needed. If your question is will the election change our response? No.
"It has to be about health, wellbeing and New Zealand's economic position before politics, every time."
POLICIES: TAX
In 2017, Labour was chock-full of policy ideas it had built up over nine years in Opposition.
Some proved unrealistic, others were unpopular, others were de-railed by the coalition agreement, or cost, or Covid-19.
One of the comparatively few policies Labour will put up is its tax policy.
Ardern says Labour will release its tax policy fairly early in the campaign: it has been used as a battering ram by National, which has claimed Labour can not afford the debt it is taking down without raising taxes.
She says the Government has already made tax changes worth $3 billion as part of the Covid-19 response, such as to provisional tax thresholds, and building depreciation.
"All of that should give people a bit of an indication of where our mind is. We want to reduce the liability for the people who are the job creators right now."
Ardern earlier ruled out introducing a capital gains tax while she was Prime Minister, and says that promise has not changed because of Covid-19.
But she will give few hints as to what else is planned, including the possibility of a new tax bracket for high-income earners.
Ardern says another controversial tax proposal from Labour's 2017 manifesto will remain off the table: the plan to levy for the commercial use of water.
It proved unpopular in the rural sector in 2017, sparking protests such as the infamous Morrinsville farmers' protest and was the first proposal scrapped in coalition negotiations with NZ First.
Ardern says the Government has completed its recently announced water reforms and there are no plans to revisit the levy.
HAS COVID-19 MADE BEING A LEADER IN CLIMATE CHANGE UNAFFORDABLE?
"Climate change is the nuclear-free moment of my generation," was one of Ardern's most famous campaign lines in 2017.
Ardern says she has no intention of revising measures decided before Covid-19 came along, such as the Zero Carbon Act, emissions trading scheme and a pricing regime for agriculture – all of which will cost the industries the economy is now most reliant on.
Ardern believes it is still fair to expect farmers to foot environmental and climate change costs, despite the economic impact of Covid-19.
She says as Covid-19 runs rampant globally, consumers will look for countries they can trust for food – and that means protecting the environmental brand.
"We want them to look to us. So now is not the time to back away from that. In fact, in the Covid environment, many of them have been doing well because of that."
She says there are other ways to relieve the cost burdens on those industries without removing environmental goals, such as employment assistance.
Ardern also still believes New Zealand can afford to be a "leader" rather than a follower in implementing climate change measures.
She says Covid-19 is helping the Government accelerate some of those measures, such as those around renewable energy as it boosts infrastructure spending.
"So no, we should not back off that ambition. Now is probably the time to speed up."
FORTRESS NZ:
Last week former Prime Ministers Helen Clark and Sir John Key both raised the prospect of starting to let more people through the border, with quarantine periods.
Asked how long New Zealand can realistically maintain current border settings, Ardern says work is under way to allow more business people and workers beyond the current "exemptions" process, while maintaining quarantine.
"We are in a position that is unlike anywhere else around the world, where our economy, domestically, is open. And the trade-off for that - and there is a trade-off - is our border controls.
"I do think that is the right trade-off because otherwise we would not be making the economic gains that would be anticipated with an open border, because there would be lockdowns.
"The question going forward is how do we make sure we can make the most of the opportunity we have of being domestically open while still having those border controls?"
2020 AND BEYOND:
If Ardern is successful, she may well return to power without at least one handbrake.
NZ First leader Winston Peters has boasted of being the "handbrake" to Ardern's change agenda.
His party's current polling remains low. Asked to rate Peters' chances of getting back in, Ardern smiles. "I've never, ever written off Winston Peters and I'm not going to start."
She has refused to set out what her governing preferences are ahead of the election, although Green Party co-leader James Shaw has made no secret of his own preference for a Labour-Green Government.
Ardern will not say whether she would happily have NZ First at the Cabinet table again, but she does argue the "handbrake" line has been overstated, and the parties actually delivered on Labour's change programme in child poverty, climate change and elsewhere.
But Ardern has clearly already considered what the fate of some of the NZ First's policies would be.
Asked if NZ First's key gain of Shane Jones' $3 billion Provincial Growth Fund would survive, Ardern says Labour would keep elements of a regional investment programme.