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The Greens will elect a new female co-leader on April 8 to fill the position that has been vacant since Metiria Turei resigned before the election, amid the benefit fraud scandal.
Party leader James Shaw says nominations will open on February 2 and close a week later.
Senior MP and Conservation Minister Eugenie Sage is tipped to succeed Ms Turei.
Two other MPs, Marama Davidson and Jan Logie, are expected to put their names forward.
Party co-leaders do not have to be MPs and anyone who has been a member for six months can be nominated.
Mr Shaw said it would be an orderly process and there would be
no comment from anyone, including the candidates, until nominations close.
Voting will be through branch delegates, and the number of delegates will be proportional to the local membership.
Each branch will have three or four delegates, and a total of about 150 votes will be cast.
Mr Shaw said a two-month campaign was long enough for members to make up their minds.