Like the prime minister, Tauranga MP and Cabinet minister Simon Bridges is voting for the alternative flag.
"I just think the current flag doesn't particularly say a lot about who or what we are as a country today," he says.
"It very much is a historic flag based on our colonial past, and I'm a real Anglophile who likes all things British from the Queen through to my wife, but I don't think the flag today represents the dynamic, multicultural country we've become."
He rejects suggestions that the referendum is a Government vanity project, saying people should focus on the vote.
"Put aside all the politics and vote on the merits of it ... I personally think if people take the politics out of it and vote on the merit, the rationale for change and the change to a more modern flag is pretty compelling."
Interestingly, the alternative design was Mr Bridges' second choice in the initial referendum last year.
He liked the colours of the red-and-blue silver fern design better, he said.
Colours aside, Mr Bridges said people should vote on the flag because the opportunity "isn't going to come around again in our lifetime".
National's Bay of Plenty MP Todd Muller is also voting for the alternative.
"I'm a great follower of history and I very much appreciate our British history as part of who we were," he says, "but I think New Zealand of today is very diverse and a vibrant country, and I think the alternative far better represents the country of today than the current flag."
Like Mr Bridges, Mr Muller initially preferred Kyle Lockwood's red-and-blue silver fern but says he is comfortable voting for Lockwood's other design now. "I think if it's chosen, over time it will become a flag that's incredibly well-loved." Mr Muller is one of several National politicians, including Mr Key, who have been wearing the blue-and-black design on lapel badges since it was chosen as the alternative, and he is unapologetic about the move. "We live in a democracy. There is a public referendum on which flag we should choose and I think individuals should be freely able to express that choice without fear nor favour."
He said he would be disappointed if a majority voted for the current flag but he would respect their choice.
"I'm a passionate New Zealander and if that remains our flag, I will continue to wear it."
Mr Muller also encouraged people to exercise their vote. "[It's] one of those once-in-a-generation questions and I think whatever the result is, the result will be stronger with a higher turnout."
Tauranga's New Zealand First list MP Clayton Mitchell is voting for the existing flag.
"I very, very strongly want to keep the flag that we've got," he says. "I think it gives us a clear direction of where we've come from and is certainly where we're going as a country."
Mr Mitchell says the flag referendum is "a vanity project of [Prime Minister] John Key". "[He] wants to have a legacy left behind that's just of what he's achieved. I think it's a waste of money the way he's gone about running a referendum."
Mr Mitchell said the Government was not known for binding referendums, giving the anti-smacking legislation and a reduction in the number of MPs in the House as examples.
"They only stick to it when it suits them," he said. "I think there's a certain feeling from people that, 'Oh, even if we do vote against [changing the flag], somehow John Key is going to wrangle it so it goes through regardless'." He called on everyone in Tauranga to vote. "If they've got a strong opinion either for or against, people just need to start having an opinion."