MPs M.A. Sumanthiran and S. Sritharan are vying for the leadership of the TNA after R. Sampanthan.
The TNA and its key affiliate ITAK hold a convention on 20 January to choose the new leader.
Sritharan is favoured for the position by the Tamil diaspora.
The elderly and ailing Sampanthan does not get involved in politics or attend parliament.
He has been under pressure by the party seniors to step down.