Ballots were due to open today for the deputy leadership of the SDLP.
About 500 delegates are expected to cast their votes over the next two days for the five candidates at the SDLP's annual conference in Newcastle, Co Down.
Stormont ministers Ms Bríd Rodgers and Mr Sean Farren, junior minister Mr Denis Haughey, North Belfast MLA Mr Alban Maginness and Down District councillor MS Margaret Ritchie are vying to replace Mr Seamus Mallon who will resign the post this weekend.
The winner of the deputy leadership contest will be announced on Sunday.
Northern Ireland Deputy First Minister Mark Durkan is also poised to succeed Mr John Hume as leader.
Mr Durkan, who was elected Deputy First Minister at Stormont on Tuesday in a controversial Assembly vote, has not been challenged for the leadership.
He will not formally accept the leadership until the deputy leadership contest is over.
SDLP sources said the deputy leadership battle was very close. "The favourites would appear to be Bríd Rodgers and Alban Maginness but Sean Farren has also performed well over the last six weeks," one Assembly member said. "It will be tight".
PA