In what could be perceived as a setback to AMMK founder TTV Dhinakaran, one of his key aides joined the MK Stalin-led DMK Friday.
V Senthil Balaji, one of the 18 disqualified AIADMK MLAs, joined the DMK in the presence of its president MK Stalin at the party headquarters Anna Arivalayam.
The defection assumes significance as it comes amid reports that Mr Dhinakaran is finding it hard to keep his flock together in the backdrop of the October Madras High Court verdict upholding Tamil Nadu Assembly Speaker P Dhanapal's order disqualifying 18 AIADMK MLAs.
Mr Dhanapal disqualified them last year for revolting against Chief Minister K Palaniswami.
Reports claim that not all the disqualified MLAs are happy with Mr Dhinakaran's decision to not to appeal against the Madras High Court order upholding their disqualification.
Mr Balaji, Transport Minister in the previous 2011-16 AIADMK government headed by late J Jayalalithaa, was elected from Aravakurichi in the Assembly polls held in 2016.
But he was not inducted in the cabinet then. Mr Balaji had represented Karur in 2006 and 2011.
Sensing the defection, Mr Dhinakaran had made a veiled attack on Balaji on Thursday, saying none will repent if some with selfish interests were to quit the AMMK.
Mr Dhinakaran, comparing dedicated party workers to "true gold," said no one will repent if gold plated "fake" were to move out of the party.
"Our foundation is Amma's (Jayalalithaa) ideals, and people's welfare is our task," the AMMK leader had said.
Without naming Mr Balaji, he said it would be better if those who held views contradictory to the goals of the party eased themselves out of the outfit.
Considered to be among those close to Mr Dhinakaran, Mr Balaji, who was AMMK organising secretary, did not take part in a party procession here to observe the death anniversary of Jayalalithaa on December 5.
Meanwhile, another disqualified AIADMK MLA, R Murugan, questioned Mr Balaji's decision to join the DMK, saying the late AIADMK chief J Jayalalithaa had to face the disproportionate assets case which was filed only by the earlier DMK government.