Bill English and Jacinda Ardern are studying for tonight's debate in what will be voters' first chance to see the leaders go head-to-head.
The hour-long event on TV1 begins at 7pm and RNZ will have live coverage online.
Labour leader Jacinda Ardern had an early "trial run" appearing on Newstalk ZB this morning with debate moderator Mike Hosking.
Mr Hosking - whose appointment as the debate's host has sparked controversy - asked Ms Ardern what she would be wearing to the event.
"Are you asking Bill that question too?" she joked.
"I want it framed in exactly the same way."
Mr Hosking said he would, assuring her there would be "balance up the wazoo".
National leader Bill English told reporters he would be wearing a suit and a brand new tie.
Asked whether he would borrow his predecessor John Key's lucky cufflinks, he said Mr Key would never part with them.
"I don't need luck the same way he did," he quipped.
Neither leader is relying on luck; both have spent days preparing, going over their notes and running practice debates.
National has engaged candidate Nicola Willis and MP Chris Bishop to stand in as substitutes for Ms Ardern during rehearsals.
Both were top university debaters, a history they share with the Labour leader.
But Mr English said he was less focused on the theatre and more on National's policies.
"My prep has been mainly getting out and about, talking to the checkout operators, the staff on the factory floor, the truck drivers, the freezing workers, the farmers."
Ms Ardern has been rehearsing with various Labour staffers, but said she was not psyching herself out.
"It's one part of a much larger campaign. I know there's been a lot of emphasis on [the debate], but this entire election campaign is important.
"Every single day our leadership is being tested as individuals. This is just one part of that."
The leaders will face off four times in the lead up to the election - twice next week and then again just three days before election day.