South Belfast MP Alasdair McDonnell is expected to announce today that he will run against Patsy McGlone in the battle for the SDLP leadership.
Nominations for the party leadership and deputy leadership were due to close today at 5pm.
So far the only declared candidate is Mr McGlone, a Mid Ulster MLA and the current deputy leader of the SDLP.
Last night Mr McGlone said that he would be standing regardless of what anyone else did, and would not be pulling out as part of any horse-trading over the weekend when nominations are in.
"My support is building," he said. "I am well over the five branches needed for a nomination. I recently got the backing of Fitzwilliam Cavehill, the second largest branch in the party."
That branch is the stronghold of Alban Maginnis, an important power-broker and opinion former in the SDLP. He would be a powerful ally if Mr McGlone secures the leadership and might be a possible choice as a minister.
Unlike other possible candidates, Mr McGlone has canvassed widely since announcing that he would run early in the summer.
This has enabled him to gauge feeling across the province. He has made no bones about the fact that he felt the party's leadership had been poor and that he was disappointed that leader Margaret Ritchie didn't make him a minister in preference to Alex Attwood.
Mr Attwood also has support, but plays down any talk of personal ambitions.
"The SDLP discussion about leadership is about how, over the next 40 years, the values that have served the people of this island so well can continue to serve the people so well," he stated in a recent interview.
He said it was "an utter irrelevance" whether he kept his Environment ministry and pledged loyalty to whoever was elected.
Dr Alasdair McDonnell was narrowly defeated by Ms Ritchie in last year's leadership battle.