Chlöe Swarbrick is defending herself against Labour rival Helen White, accusing her of using "the same attacks against me that misogynists do our PM".
Swarbrick is running as the Green Party candidate for Auckland Central. Current electorate MP Nikki Kaye, who is leaving politics at the end of this term, has only managed to hold the seat for National because the Greens and Labour candidate vote was split.
Winning Auckland Central could ensure the Greens' survival if they fail to break the 5 percent threshold to return to Parliament. And with Labour's coalition partner NZ First struggling in the polls, the return of the Greens could be key to keeping the centre-left in power this September.
But Swarbrick faces fierce competition from Labour's candidate Helen White who is refusing to stand aside in an election deal.
Speaking to RNZ earlier on Sunday, White said the gap in 2017 votes between Labour and National compared to the Greens and National means it makes sense for Swarbrick to drop out, not her.
"The vote was so close for Labour, it just isn't in the same league with regard to the gap that the Greens would have to move," she said.
But the Greens disagree, saying they have a better chance of winning the seat.
"We think that Chloe can win on her own merits," party co-leader James Shaw told Newshub Nation on Saturday.
"She is an extraordinary candidate, she's got an enormous profile, she certainly has the highest name-recognition in that electorate. National don't even have a candidate there at the moment. We think she can win it, and we're throwing everything at it."
White fired back when questioned what she'd say to people who ask about Swarbrick's higher name recognition, telling RNZ: "I'd ask them whether they're looking for a celebrity or someone to do this job very seriously."
This barb led to a sharp jab from Swarbrick, who took to social media to defend herself.
"Before I fought my way into @NZParliament with @NZGreens, I was dismissed as having no life experience," she tweeted on Sunday.
"Now I've put my head down and done the work to huge results, and a candidate preferring themselves the front runner is using the same attacks against me that misogynists do our PM?"
While Jacinda Ardern has a positive profile both in New Zealand and internationally - with particular praise for her communications skills, some critics have accused her of being a lightweight with a focus on appearance over substance.