The Green Party believes Jacinda Ardern's elevation to Labour's leader is an election game-changer.
Greens co-leader James Shaw said Mr Little did the right thing by stepping aside.
He said it changes the shape of the whole election campaign and gives Labour and the Greens a real chance of forming a ruling coalition.
"I think she's got the skills, she's got the leadership capability, she's got the connection with the public. This is a very different kettle of fish to how it was last week.
"I think today's announcement definitely improves the chances that we will be able to change the government, and form a new government together after the election."
Mr Shaw said Ms Ardern has all the qualities needed to change Labour's fortune, change the government and become the next Prime Minister.
