In this Indian Express article, IDFC Institute's Praveen Chakravarty, Swapnil Bhandari and Rithika Kumar write on the return of Jayalalitha as Tamil Nadu Chief Minister, and implications for politics going forward:

"In the nearly 30 years since the death of former Chief Minister M.G. Ramachandran and the advent of Jayalalithaa, the AIADMK and the DMK, led by M. Karunanidhi, have ruled Tamil Nadu alternatively, mostly in five-year terms... The combined vote share of the AIADMK and DMK fell to its lowest in the 2014 general election. In 1991, when voters had a choice between a DMK or an AIADMK candidate, 91 out of every 100 voters chose one of the two parties.

In 2014, only 71 out of 100 chose one of the two, with nearly 30 choosing a non-AIADMK/ non-DMK party. In the 2011 assembly election, the combined vote share of the AIADMK and DMK was 86.3 per cent, the lowest in 20 years. It is irrefutable that fewer and fewer voters choose one of the two main parties. However, it is also pertinent that while the vote share is certainly declining for the two major parties in Tamil Nadu, the entire non-DMK/ non-AIADMK voter base at its peak is still only 30 per cent...

So, to unseat either party, a combined third front will need a vote share greater than 50 per cent. The current levels of 30 per cent are inadequate. While the winning vote share percentages of the two parties have been declining steadily, it is not low enough yet for any united third front to unseat the incumbents...."