Social Democratic and Labour Party (SDLP) MP Alasdair McDonnell has written to the party's branch chairmen inviting them to nominate him for the leadership if a contest is held.
It follows an announcement by the SDLP deputy leader Patsy McGlone that he is going to challenge leader Margaret Ritchie in November.
Dr McDonnell was unavailable to comment on his letter, but some SDLP sources are tipping him to perform strongly in a competition.
He stood for the leadership last year, but was narrowly defeated by Ms Ritchie.
Earlier this month, Mr McGlone confirmed he will seek the party leadership this autumn. Ms Ritchie also made clear her intention to run.
Five branch nominations are required to contest the leadership. Just under 350 delegates are eligible to vote in a ballot, which would be held at the annual conference in November.
Ms Ritchie became leader in 2010, beating the only other candidate - South Belfast MP Dr McDonnell - by 35 votes.
Her critics have blamed Ms Ritchie's style of leadership and media performances for the party's poor assembly election results in May.
Mr McGlone confirmed he would challenge the SDLP leader at the beginning of August. He said he had been encouraged to do so by friends and colleagues.
Environment Minister Alex Attwood has backed Ms Ritchie's leadership.