Mr Tipene did not return calls yesterday but the party president Pem Bird said it was clearly a reference to Tariana Turia over her comment in the lead-up to the byelection that Mr Harawira should win it, if he had put in the work.
Mrs Turia later apologised for the comment both publicly and to Mr Tipene.
Mr Bird said he was disappointed by Mr Tipene's "inexcusable" outburst, given the time and resources the party had put into his campaign.
Mr Shortland said he understood Mr Tipene's frustration and there was clearly some "residual pain". Mr Shortland said he had checked with Mr Tipene before he put his own name up, because he did not want to run against one of his own iwi.
He said Mr Tipene had indicated he would be supportive of him.
Mr Tipene's focus was to make life harder for Mr Harawira.
"I don't believe he should have a free ride and in the final analysis it would be a huge prize if there was no Mana."
A spokeswoman for the Maori Party said the leaders would not comment on the matter. Mrs Turia was recovering from concussion after a car accident this week.