The elevation of M.K. Stalin as the working president of the Dravida Munnetra Kazhagam achieves two objectives.:

1. It fills the power vacuum at the top following the prolonged illness of party president M. Karunanidhi . 
2. Provides an opportunity for the DMK to take advantage of the fluid political situation in Tamil Nadu after the death of Chief Minister Jayalalithaa and the prevailing confusion within the ruling AIADMK on whether O. Panneerselvam should make way for V.K. Sasikala as Chief Minister. 

Advantage to DMK:

The DMK is currently in a politically advantageous situation; it had lost the Assembly election narrowly, and its main rival now is in some disarray
The AIADMK without Jayalalithaa faces a stern test. It helped that the party was in power when she died; otherwise, the district-level leaders might have begun pulling in different directions whether or not Ms. Sasikala became the general secretary. However, there is strong sympathy wave with AIADMK on account of death of Jayalalithaa.

Background of M.K. Stalin:

Muthuvel Karunanidhi Stalin is better known as M. K. Stalin, who was Deputy Chief Minister of Tamil Nadu from 2009 to 2011. Stalin is the third son of famous Tamil Nadu politician Karunanidhi, and was born to his second wife, Dayalu Ammal.