Here are the 10 latest developments on this story:
Sources said the immediate strategy of Mr Panneerselvam or OPS, as he is called, is to win over a few more legislators from the Sasikala camp; just enough to ensure that she does not have the 117 needed for a simple majority in the 235-member Tamil Nadu assembly.
Mr Panneerselvam, asked by the Governor to stay on as interim chief minister after his resignation was accepted last week, is likely to attend office today. Journalists have alleged attack by goons near the resort where AIADMK MLAs are camping. Mr Panneerselvam has promised strict action into the matter.
Ms Sasikala, who visited the Chennai resort twice over the weekend, has said she expects a call from the Governor today. The AIADMK general secretary staked claim to form government on Thursday, stating that she has the support of over 129 of the party's 134 MLAs.
Among those who have crossed over the Panneerselvam camp is the state's education minister, K Pandiarajan. Mr Pannerselvam has also acquired the crucial support of 11 members of Parliament, senior leaders with influence in the party.
Ms Sasikala invoked former chief minister J Jayalalithaa in her speeches at the resort, where she invited the media to "see for themselves that the MLAs are free and happy." While they appeared on camera, no legislator spoke. However, few who had spoken on Saturday claimed they stayed voluntarily, paying from their pocket, to prove majority whenever the Governor calls.
Governor Rao, sources have said, is not inclined to invite Ms Sasikala to form government before a Supreme Court verdict likely this week, in a corruption case against her. If guilty, Ms Sasikala will not be allowed to hold public office or contest elections for six years.
Ms Sasikala is not a legislator - she has never contested an election within or outside the party - and if she is sworn in chief minister, will have to contest and win an assembly seat within six months.
The Centre has supported Governor Rao on his wait and watch strategy. "The governor has to follow procedure. The centre has no role to play in this," said Union Minister M Venkaiah Naidu. Sources close to the Governor said on Sunday that he "won't be intimidated" by Ms Sasikala's efforts to expedite her swearing-in.
Mr Panneerselvam has alleged that he was forced to resign as chief minister to facilitate a takeover of the top post by Ms Sasikala, Jayalalithaa's closest aide for three decades till she died in December. Both claim rights to Ms Jayalalithaa's legacy and the party, attacking each other as "betrayers" of Amma, as Ms Jayalalithaa was known to her supporters.
Main opposition party DMK has asked the Governor to ensure Tamil Nadu gets a stable government at the soonest. Amid the political crisis, the DMK's high-level executive will meet today.
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