Moving into Premier House this weekend, the Prime Minister will find her in-tray filled to overflowing.
Her brief parental leave break will quickly be forgotten with the range of issues requiring her attention. This is not to suggest that the wheels of government have been stuck with Winston Peters in charge. Indeed it would be hard to fault Peters' performance, though he was rarely tested by his opponents or required to make any big calls.
The country is not yet 12 months into the three-year electoral cycle but it is far enough along the track for Ardern to know she has her work cut out to keep Labour in office.
How she comes through 2019, before sentiment consolidates from the start of 2020 when the election is due, is a vital test.
The reality is that the fortunes of the Coalition rest largely on her personal popularity. If she remains a popular figure, then there is every chance that the Coalition will also stay match-fit.
The new mother will need to hit the ground running. The fact that Clarke Gayford is to be a stay-at-home father with their daughter Neve, gives Ardern a little more clear air to manage the issues piling up at the Government's door.
Her time away has coincided with a souring of business confidence, which in turn has handed National under Simon Bridges a gift to hammer away at Government competence.
The level of negative sentiment was last recorded a decade ago when the world economy was reeling from the global financial crisis, New Zealand was in recession and Parliament passed a law to protect bank deposits. In contrast the current domestic fundamentals appear solid. Growth is around 2 per cent, employment is robust and immigration, though below the record flows of recent years, remains strong.
Beyond the noises of surveys there has nonetheless been real-world pain. The collapse this week of the construction firm Ebert will reverberate widely. No doubt another firm will take up the slack, but there is certain to be damage along the way.
In the workplace, nurses appear likely to accept the settlement coming their way. Now it's the turn of teachers to push for more, while the police force has made it clear they are unhappy with their pay packets.
These demands, even if partially met, will take a chunk of Government revenue, and require a readjustment of the budget. Any deals may also embolden other groups to demand pay rises, at a time labour laws may tilt a little towards the unions — a prospect which further alarms business.
International forces may ultimately be more telling on the Government's political fortunes. China's economy, trade wars, export prices and the sharemarket's direction all have the potential to impact on New Zealand.
It may be that the return of Ardern revitalises key figures — such as Finance Minister Grant Robertson — which in turn lets the Government project an image of unity and competence. These signs have not been at all clear since the Prime Minister took her leave.