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She is down 15 percentage points in the preferred prime minister rankings in tonight's 1News/Colmar Brunton poll.
Ardern is sitting at 43 percent - which is still significantly higher than her main rival, National's Judith Collins, who's at 8 percent - down 4 percentage points on the last poll.
Meanwhile, former leader Simon Bridges has appeared on that list - sitting at 1 percent. But he is behind National's Chris Luxon, who's at 2 percent.
The Labour Party is down 4 percentage points to 49 percent - that's far ahead of National's 27 percent, which is up 2 percentage points.
In terms of seats in the House, Labour still have a majority with 62 seats.
The Greens are up slightly to 9 percent and Act is steady at 8 percent.
The Māori Party is up to 2 percent, the poll shows.
Speaking to TVNZ, Ardern said she was still pleased at the level of support she is getting.
"I do have to make some tough calls and they do impact on people's lives, but I still feel really heartened to have the support too."
On the increase from 25 percent to 27 percent, Collins said National was beginning to "trend a little bit in the right direction".
"But there's a lot more work to do," Collins said.
Asked if she was nervous about a leadership challenge based on her preferred PM rating being in single digits and her party in the 20s – Collins said, "not at all".
Tonight's poll is the first since December last year. Those numbers showed that Labour had a commanding lead over National. Labour was sitting at 53 percent while National was at 25 percent.
The December poll was taken roughly two months after the election where Labour won an outright majority in the House and formed a Government.
On that poll, both Act and the Greens were at 8 percent and the Māori Party was on 2 percent.
New Zealand First, which was booted out of Parliament by voters at the election, was on 2 percent.
Since the last poll, Auckland has been into lockdown twice after Covid-19 was discovered in the community.
In the past, voters have been supportive of Ardern's leadership through these times.
However, in the most recent lockdown – when Auckland went to level 3 for seven days – questions were raised about the Government's communication.
Even Brian Roche – the man appointed to chair the group which monitors the Government's Covid-19 advice – said there was "mixed messaging" at play.
This has been an issue that National has been critical of the Government over.
Tonight's poll is the first 1News/ Colmar Brunton poll not to use landlines.
In the past, there had been a 60/40 split – but tonight's numbers won't include a single poll taken from a landline.
Tonight's poll was done using 50 percent randomly generated mobile phone numbers and 50 percent online from New Zealanders who have signed up for market research studies.
"People just aren't using landlines like they used to," said 1News political editor Jessica Much McKay.
"Pollsters are finding people pick up their mobile phone more regularly so it's easier to get in touch."