The former Cook Islands Prime Minister, Sir Terepai Maoate, has been called on to throw his support behind the man who beat him for the Democratic Party nomination in the constituency of Ngatangiia.
Sir Terepai had held the seat for 25 years and had been renominated in May.
However, Mann Short forced a new vote by party members and Thursday night he narrowly defeated Sir Terepai, winning 172 votes to his 162.
Our correspondent, Florence Syme Buchanan, says Mr Short has already called for the two groups to put aside their differences and come together as next month's election approaches.
"Mann is confident that the Party will come together but what remains to be seen and heard from Sir Terepai is his public declaration that he will put his weight behind Mann Short and the Democratic Party and support Mr Short in the forthcoming elections."
Florence Syme Buchanan.