The contenders:

GRANT ROBERTSON

Labour’s deputy leader is shaping as the favourite to take over from David Shearer. Mr Robertson is a career civil servant and former diplomat who worked for former prime minister Helen Clark and the Labour Party for a number of years before becoming an MP. The rugby-mad gay MP is well liked within the party, but not well known outside Wellington.

DAVID CUNLIFFE

The Harvardeducated former Cabinet minister unsuccessfully contested the leadership when Phil Goff stepped down after the 2011 election. In 2012 he was demoted from the front bench for not expressing support for his leader. He is seen as having the intellect required for the leadership role but, while popular with the wider party, he is not well liked in the caucus – a faction known as ABC (anyone but Cunliffe) backed Mr Shearer instead.

ANDREW LITTLE

A newcomer to parliamentary politics but already tagged as a future leader, Mr Little has a long history with the unions and is a former Labour Party president. The former student politician served as head of the Engineering, Printing and Manufacturing Union for 11 years. A lawyer, he stood for Parliament in the New Plymouth electorate in 2011 but was thumped by National’s Jonathan Young.

Possible deputies and wildcards:

ANNETTE KING

The darling of the Left, Ms Ardern is a young star on the rise. A former Young Labour member who worked in the offices of Phil Goff and Helen Clark, she returned from a spell in London after being ranked 20 on the party list in 2008, guaranteeing her a place in Parliament. In 2011 she ate into Nikki Kaye’s majority in the Auckland Central electorate, in what was otherwise a disastrous election for Labour.

JACINDA ARDERN

Something of a grandmother figure within Parliament, Ms King entered the House in 1984 and has been there ever since, but for a single term in 1990-1993. A former dental nurse, she originally represented Horowhenua before moving to the Miramar seat (now Rongotai) in 1993. Health minister under Helen Clark, she returned to the portfolio last year and has landed more blows on the Government than many colleagues.

DAVID PARKER

Winning the otherwise safe National seat of Otago to enter Parliament in 2002, the former litigation lawyer and businessman rose to be attorney-general by 2005. He quit a year later after an allegation that he had filed an incorrect declaration with the Companies Office, although an inquiry later cleared him. He has revamped Labour’s economic policy with a capital gains tax, monetary policy reform, and a move to lift the pension age over time. Briefly put his hat in the ring for leader in 2011 before pulling out.