Yet she says she did not consult with Cunliffe before making her decision.
Cunliffe had already given his endorsement to Andrew Little by then and did not change that after Mahuta entered. Mahuta said she had not asked him to.
She will not say whether she was disappointed Cunliffe had pulled out or whether it would have been difficult in caucus for him to stay on.
"His decision around the leadership was his. I had no influence over that."
However, she said he had faced "real challenges" in his year as leader and makes it clear they were from within Labour.
"His closest supporters understood the extent of those challenges, but he didn't let it deter him from trying to do the best job he could do to get into Government in 2014. You do what you've got to do. He was focussed on looking in front of him, but it is hard if leaders are having to look behind them as well."
She insists she is not simply positioning for deputy. "People will be assessed on their merits and ability to contribute. If I'm not successful it's up to the leader to decide."
Mahuta will almost certainly not win, meaning the second choices of her supporters will come into play under Labour's preferential vote system. She said she would decide who to advise her supporters to give their second votes to after listening to what the other candidates had to say.
"We are sitting at 25 per cent. There are huge perceptions about whether or not Labour can pull it together in the caucus. There are huge perceptions we are no longer relevant to communities."
However, like Shane Jones' run for the leadership last time round, but for different reasons, Mahuta has nothing to lose from contesting it.
It also helped Labour in a way - no longer could its leadership lineup be described as three middle-aged white men. When I say she's a gutsy woman, she replied "got to give it a whirl."
Mahuta is mother to two young children responsibilities outside Parliament with Tainui. Asked whether she'll cut some of her tribal work if she is leader, she said she is a woman "and women multitask".
"Women can do amazing things and still continue to be mums."
She said she would wind back some of the tribal work if she was leader.
Little known fact: She has tattoos of her children's names on her feet.
