Labour MPs arrive at Parliament ahead of a caucus meeting to decide leader Andrew Little's future.
Jacinda Ardern has had a steady rise through the ranks of the Labour Party since entering Parliament in 2008.
Ardern was born in Hamilton in 1980, attending primary and secondary school in Morrinsville and also spending a few years living in Murupara, where her father was a policeman.
She joinedLabour aged 17. She grew up in a Mormon household but left the faith in her 20s, mostly because of its anti-homosexual stance.
After completing a Bachelor of Communication Studies at Waikato University, Ardern worked for Phil Goff and Helen Clark.
She spent three years in London as a policy advisor in the UK Cabinet Office, and in 2007 was elected president of the International Union of Socialist Youth.
Labour Party MP Jacinda Ardern is tipped to be her party's next leader. Photo / Mark Mitchell
Ardern, who has cited Clark as a political hero, stood for Labour in Waikato in 2008 and entered Parliament as a list MP. She was narrowly defeated by now Education Minister Nikki Kaye in Auckland Central in 2011 and 2014.
After moving into Mt Albert with her partner, broadcaster Clarke Gayford, Ardern stood in and won the Mt Albert byelection in February, prompted by the resignation of David Shearer.
Her strong showing in that contest saw speculation she would be elevated to the deputy leader position. After Annette King stood down from the position Ardern was elected unopposed by Labour's caucus. At the time, Andrew Little said it was partly because of her ability to reach a group of people the party needed to connect with better - young and urban.
Ardern has never stood for the Labour leadership in the three contests since 2011 but she was on Grant Robertson's unsuccessful ticket as deputy following the 2014 general election.
She is spokeswoman for justice, children, arts culture and heritage, and small business, and associate spokeswoman for Auckland issues.
Ardern has steadily risen in preferred Prime Minister polls - out-performing Little - and is the highest-ranked Opposition MP by chief executives surveyed in the Herald's Mood of the Boardroom.
