Mr Denis Haughey, a junior minister in the Stormont Executive, announced this afternoon he would be standing in the contest for SDLP deputy leader.
The MLA for Mid Ulster said "I believe I have the experience, the capacity and the energy to play a key role in our work to create a new Ireland and a renewed SDLP."
Mr Haughey claimed discussions with party members have convinced him he will attract widespread support in the ballot.
He added "I want to work with the new leader to strengthen the organisation, improve our decision-making process and work closely with branch members."
Stormont Agriculture Minister Ms Bríd Rodgers was today preparing to say whether she will also seek the deputy leadership.
Sources close to the 64-year-old Upper Bann MLA said she was coming under pressure to succeed Mr Séamus Mallon, who quit as deputy leader on Tuesday.
"Bríd has been thinking long and hard about what she might do in the wake of John and Seamus's decisions to stand down," a party source said today.
"She has been contacted by a number of branches about putting her name forward for the deputy leader's post and is weighing up the arguments. There should be a decision from her today on what she intends to do".
If Ms Rodgers stands, she will be the second candidate to declare for the deputy leadership of the SDLP.
Former Belfast lord mayor and North Belfast MLA Mr Alban Maginness announced on Tuesday night his intention to run.
Other possible candidates for the post of deputy leader include Employment and Learning Minister Mr Sean Farren, South Down MP Mr Eddie McGrady and Assembly members Mr Joe Byrne, Ms Patricia Lewsley and Mr Eamon O'Neill.
There was also growing speculation in the party that Mark Durkan, the 41-year-old finance minister, will have a clear run for the leadership at the SDLP's annual conference on November 9th.