Green MP Nandor Tanczos, making his last bid for the co-leadership today, wants the party to drop its ban on propping up National-led governments.

The Greens have traditionally ruled out supporting a National-led government, but the list MP believes this may have painted them into a corner and says the party may need to adopt a more "independent" position.

It is one of the platforms Mr Tanczos has been campaigning on during the run-up to today's vote in the Hutt Valley on the male co-leader's job, which will fill the vacancy left by Rod Donald's death.

Delegates from 60 electorates will have the final say, with most set to arrive with voting instructions but some open to being swayed by last-minute presentations.

Mr Tanczos and the party's election campaign manager, Russel Norman, are considered the front-runners, although Dave Clendon is believed to have strong support in Auckland.

Former Green MP Mike Ward is the fourth candidate.

Mr Tanczos said the party had been right to rule out working with National last election because of the political agenda of its leader, Don Brash.

"But my own view is that in the longer term we should support parties where we can find policy agreements.

"So if we can work out an adequate policy agreement with the National Party, then I certainly think we should sit down and talk with them."

The two parties differed strongly on a number of social and environmental issues but "it's quite conceivable that in 10 years the National Party is going to look very different from what it looks like now".

Asked if he would advocate not ruling out working with National if it was led by Dr Brash at the next election, he said, "I'm not making any comment about the next election because I don't know what National is going to look like, but what I'm saying is that in the medium to long term the difference between National and Labour is going to become increasingly difficult to distinguish."

Mr Norman said the party worked "issue by issue with everyone".

"In terms of coalitions, it's very difficult at the moment to see how we'd work with National because of their position, particularly on climate change, where they're still climate change deniers, it seems.

"Generally we're closer to Labour, but Labour and National are closer to each other than to us."

It was "hard to see" the Greens supporting a National-led government at the moment "but issues have to be the bottom line".