"What this means now is even more uncertainty over what a Labour-led government would look like. With Labour in chaos, and with an inexperienced leader, Winston Peters and the Greens will be able to extract major concessions after the election.
"Will benefit fraudster Metiria Turei demand to be the Minister for Social Development? Will the price of Winston Peters' support be the Prime Ministership? These questions should give New Zealanders cold sweats."
Green leader Metiria Turei took to social media thanking Little for the work he has done for the country.
New Zealand First leader Winston Peters sympathised with Little, saying "politics is a tough business".
"He's fought the good fight, but at the end of the day he was a victim of the transience of the polls.
"We can say what we like about polls, but at the moment the picture is bleak for a number of parties.
"Jacinda and Kelvin will know that they have taken on a big job, some will say an insurmountable task, but we tender our congratulations."
United Future leader Peter Dunne appeared stunned by Labour's decision.
Maori Party co-leader Marama Fox believed the decision showed Labour is scrambling just seven weeks out from the election.
In contrast to Fox's comments, Maori Party President Tuku Morgan has called on Ardern and Davis to work with the Maori Party for the best interests of New Zealand.
He said Little "killed off any hope" of the Maori Party working alongside Labour.
"Maori people throughout the country are telling me they want our party to work with Labour if it's in a position to form a Government after September 23.
"We've always said we'd work with both sides, blue or red, but Andrew Little killed off any hope of that happening when he closed the door on us.
"We're hoping Jacinda and Kelvin won't be as closed-minded and that they'll agree to work with kaupapa Maori.
"Like Labour, our party is concerned about more than half the prison population being Maori, not enough Maori people owning their own homes, Whanau Ora not getting enough funding to make the difference we want it to and the shocking number of people sleeping in their cars and on the streets.
"For the sake of those people, we need to work together or at least have a proper and meaningful discussion about it."
Ardern also paid tribute to Little, thanking him for giving her the chance at working alongside him in a leadership position.
Davis is believed to be the first Maori to hold the deputy leader post in the Labour Party.
It follows a turbulent week for Labour in which three polls put its support in the low 20s. Little stepped down from the leadership, saying he had to take responsibility for the result.