Simon Bridges is so off-putting to voters that replacing him with a relative unknown might work in National's favour, according to political scientist Bryce Edwards.
Todd Muller, the party's spokesperson for agriculture, biosecurity, food safety, and forestry, is trying to topple Bridges, saying they can't win September's election with him at the helm. Backing Muller is Nikki Kaye, who's actually been an MP twice as long as he has and has twice defeated Jacinda Ardern in electorate battles.
Though Friday's vote is expected to be close, Dr Edwards is tipping Muller to win.
"I think the momentum is with Todd Muller at the moment just because this is just so damaging for Simon Bridges and his caucus colleagues can see that. They want to try something new."
The Newshub-Reid Research poll this week had National 26 points behind Labour - a deficit unseen since the days Sir Bill English went up against Helen Clark in the early 2000s.
Dr Edwards said many backbenchers will be worried about losing their jobs.
"Those backbenchers can see that a future under Simon Bridges isn't particularly bright. Even if Simon Bridges wins... he's going to be much more damaged than before."
Bridges, who has led the party for two years, is languishing on 4.5 percent as preferred Prime Minister. Dr Edwards says it almost doesn't matter who replaces him.
"The argument against him is he's putting off potential National voters at the moment - it doesn't matter if Todd Muller isn't that well-known, it doesn't matter if he doesn't win over voters - at least he's not putting off voters and the National brand itself is going to do the heavy lifting."
The polling also asked voters to describe Bridges in a single word, and the results were overwhelmingly negative - 'idiot', 'annoying', 'useless' and 'dickhead' featured prominently.
Bridges made the surprise move on Wednesday to reveal there was a challenge underway, and that a vote would be held on Friday. Dr Edwards suspects he's deliberately timed it to be after the release of Colmar-Brunton's latest poll on Thursday night - hoping if the numbers are better than the Reid Research poll, he'll get a stay of execution.
"He's holding out that the Newshub poll was just an extreme aberration."
Plenty of time for Muller
When Newshub hit the street on Thursday, we found few people recognised Muller. Others on social media have noted the National Party has a lot of male, middle-aged, balding white MPs.
Richard Shaw, a politics professor at Massey University, thinks four months is "plenty of time" for Muller to make his case to the New Zealand public, should he become leader.
"There will be a significant number of people who are unhappy with the tone and tenor of Bridges' leadership, but who are, at heart, National Party voters."
Ardern polled at 59 percent in the preferred Prime Minister poll.
"Time is not the issue for him," said Prof Shaw. "The issue for him is that he has a behemoth in the form of the Prime Minister."
Veteran political reporter Richard Harman, editor of political news site Politik, told The AM Show Muller would appeal to more swing voters than Bridges, whom might have taken the party too far to the right. He dismissed suggestions Muller and Kaye's more liberal views - particularly on the environment - might struggle to differentiate them from Labour and the Greens.
"They're not going to get them back by appealing to the extremes. This election, as every New Zealand election is inevitably fought, in the middle of the road."
Dr Edwards says it's hard to tell if swing voters will be convinced to give their vote to a more liberal National Party.
"Certainly Todd Muller and Nikki Kaye are more liberal than Bridges and Bennett, and that's the pitch they';re making - that Bridges is taking the party too far to the right."
Does Bridges have a future if he loses?
Harman told The AM Show Bridges should look to Sir Bill for inspiration.
Sir Bill led National to a crushing defeat in 2002, and stepped aside in 2003 to make way for Don Brash. Later on he came back as Finance Minister under Prime Minister Sir John Key, eventually taking over the top job when Sir John retired from politics.
Bridges potentially has decades ahead of him in politics - but Harman doubts he has the patience, and expects him to fight to the end to stay leader.
"He most certainly is a scrapper - he's abrasive and he can be quite aggressive. But the question is, if he wants a long-term future in politics, then the model is Bill English, who stepped aside for Don Brash, came back as Finance Minister then eventually got the leadership."
