Here are the 10 latest developments on this big story:
Ms Sasikala indicated that she had the support of 129 legislators. "You 129 MLAs are like an ocean. None can contain you by building a check dam. No efforts will destabilise this government," she said, addressing the legislators at the resort.
Ms Sasikala, 61, who had earlier in the day said that it was "very difficult" to be a woman in politics, was seen fighting back tears as she invoked former Ms Jayalalithaa, who died in December. "People who had betrayed Amma are standing against us today," she said.
Five more legislators crossed over to her rival faction, taking the number of parliamentarians in Mr Panneerselvam's favour to 10. However, the number of legislators on his side remained officially at six, including the 66-year-old himself.
"Shedding crocodile tears, passing new remarks every day is not going to help. We will prove everything in the Assembly," Mr Panneerselvam said on Sunday, alleging that the legislators were being held hostage by Ms Sasikala's camp with threats to their families.
The centre, meanwhile, came out in support of Governor C Vidyasagar Rao, who has been criticised by those supporting Ms Sasikala for delaying her swearing in. "The Governor has to follow procedure. The centre has no role to play in this," union minister M Venkaiah Naidu told NDTV.
Sources close to the Governor said he "won't be intimidated" by Ms Sasikala's efforts to expedite her swearing-in. He has so far refrained from inviting her due to a corruption case against her, in which a verdict is expected later this week.
If convicted, Ms Sasikala will not be able to stand for elections for six years. If she does become Chief Minister, she will have to contest and win a seat to the state Assembly within six months.
Last Sunday, Mr Panneerselvam had offered his resignation from the chief minister's post. While he was understood to have stepped aside for Ms Sasikala, the closest confidante of Ms Jayalalithaa, he announced two days later that he had been forced to resign.
The turnaround commissioned a sprawling political crisis in the state over days with both sides claiming rights to Ms Jayalalithaa's legacy and the party.
While Ms Sasikala claims support of an overwhelming majority of legislators, Mr Panneerselvam maintains if allowed to choose, many would back him. The Tamil Nadu assembly has 234 members and to be chief minister, a leader has to prove the support of 118 lawmakers. This time, however, the numbers would reduce by two, excluding the seat left vacant by Ms Jayalalithaa and the Speaker.
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