Deputy Labour leader Grant Robertson is the first contender to confirm he will contest the leadership following David Shearer's resignation last week.
Mr Robertson confirmed the decision to the Herald late this afternoon.
He said he decided to run, "because I think I can unify our party, I represent a new generation of leadership, and because I believe I can lead us to victory in 2014".
Wellington Central MP Mr Robertson's announcement comes as little surprise given expectations the Labour leadership race would come down to him and New Lynn MP David Cunliffe.
Mr Cunliffe did respond to the Herald's messages today but his wife said he was still making his mind up. He, and any other contender, have until 10pm tomorrow to confirm their bid.