Why did Jacinda Ardern become leader of the New Zealand Labour Party in 2017?

Jacinda Ardern became the leader of the New Zealand Labour Party in 2017 due to a crisis in the party's electoral prospects. As the September 2017 general election approached, the party's support in preference polling had fallen to abysmal levels, dropping below 25 percent in July.1

Facing this decline, the incumbent leader, Andrew Little, decided to step down. He secured a pledge from Ardern to stand as his replacement—a role she reportedly declined seven times before finally agreeing. Following Little's resignation, Ardern ran unopposed and was elected leader on August 1, 2017. Her rise to the leadership followed her earlier unanimous election as the party's deputy leader, which occurred after the resignation of Annette King.1