MPs have until 10pm Monday night to declare their intention to run. The leader will be elected by ballot, with 40 per cent of votes coming from the Labour caucus, 40 per cent from party members and 20 per cent from unions.
Speaking on Q+A this morning, Labour Party president Moira Coatsworth said it was too early to be looking at poll results, as the candidates had not yet been confirmed.
"I don't think people will have been giving this much attention so far, so let's wait and see when we know who the candidates are and they're really up and campaigning."
Former party leader Mike Williams denied suggestions former Prime Minister Helen Clark was involved in Mr Shearer's departure, saying he was in regular contact with her, and while she had an opinion she was not involved.
"She doesn't try to manipulate matters from New York the way John Key thinks she does."
Political scientist Jennifer Curtin said having grass-roots party members in the leader race could benefit Labour by having a flow-on effect on turnout for the general election.