ACT leader David Seymour has flatly rejected the possibility of becoming Deputy Prime Minister under a National Government, saying he prioritises his "independence" over the materialistic "guff" associated with a higher political rank.

On Tuesday, Opposition leader Judith Collins revealed she is considering Seymour, 37, as a possible deputy if National takes the reigns from Labour in the upcoming election - and forms a coalition with the minor party.

ACT has enjoyed a rapid rise in popularity among voters, with the latest Newshub-Reid Research poll placing the party at 6.3 percent - up by three points - after polling at just 0.5 percent of the vote in 2017. The data indicates ACT will easily meet the 5 percent threshold required for a party to make it into Parliament.

Yet speaking to Magic Talk's Road to the Election host Mitch McCann on Sunday, Seymour said "no" when asked if he wanted the coveted Deputy Prime Minister role.

When McCann pushed the topic, asking if Seymour would turn down the position if it was offered to him, he conceded that would likely be his response - but he wasn't ruling it out.

"I think that's a scenario that you may well see. If you look at the End of Life Choice [Bill], John Key asked me to be a minister - I looked at the limo, the pay rise, the title, all the guff that a lot of people spend their political career trying to get - and I asked, 'Well, can I make a bigger difference for New Zealand by maintaining some independence?'" he told McCann.

"And the effect at the End of Life Choice - assuming [the Bill] goes through and people vote for compassion on this referendum - is that thousands of New Zealanders will have control and dignity at the end of their life. That's more important to me than any title."

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He also argued it was "far too premature" to discuss positions ahead of the October 17 election.

"I'm not obsessed with where I sit on the bus," he reiterated. "[But] I'm not ruling it out."

Seymour added that ACT holds an important role in the upcoming election, as its policy would help "change the direction" of a National-led Government - revealing the reason why he was never interested in joining the party.

"At this point, we need ACT to help win the election... ACT rising in the polls, National rising in the polls - that is the key to a change in Government, but ACT's role in that is the key to a change in direction," he said. 

"One thing about the Nats - and why I never joined them - is they've been in power for 48 out of the last 71 years, and still haven't reversed a Labour policy. I just ask, what's the point in campaigning against Labour and telling everyone how terrible they are, if you're just going to be custodians of their ideas?"

"I'm not obsessed with where I sit on the bus,"

However, it's not the first time a politician in a leadership role has suggested they didn't want the top job.

In July, Collins told Magic Talk she was "very happy" with her roles in the caucus - which included spokesperson for regional and economic development - and was happy to sit back and support former National leader, Todd Muller.

"It's not something I'm ever going to go and bust a gut to get to be," the Papakura MP told Sunday Cafe host Roman Travers.

Yet just over a week later, Collins successfully succeeded Muller when he resigned from the leadership role after less than two months at the helm. 

According to the latest Newshub-Reid Research poll, 37 percent of ACT's voters have come over from National this year - while 10 percent of voters have transitioned from the Māori Party, Seymour pointed out.  

National is currently sitting on 29.6 percent, up by 4.5 points. On the basis of these numbers, neither National or ACT would hold enough of the vote to form a Government. 

ACT is now fighting with the Greens to become Parliament's third-largest party. The Greens are sitting at 6.5 percent in the Newshub-Reid Research poll, but its ally, Labour, is on 50.1 percent - meaning it could govern alone.

Yet the data hasn't stopped Greens' co-leader, James Shaw, from dreaming of a Labour-Greens Government, after the latest Colmar Brunton poll showed Labour at 47 percent - indicating a Greens' coalition and Shaw potentially becoming Deputy Prime Minister weren't "out of the realm of possibility", he said.