Political Consultant here, electoral history of TN
1962 Elections
Winning Party : INC+
Seats won:139
Vote %:46%
Runner up: DMK+
Seats won:61
Vote %:44.8%
1967
DMK+ 179 52.6%
INC+ 51 41.1%
1971
DMK+ 205 54.3%
INC+ 21 38.2%
1977
ADMK+ 144 33.5%
DMK+ 48 24.9%
INC+ 32 20.4%
JP+ 10 16.3%
This was a great 4 way fight
1980
ADMK+ 162 48.9%
DMK+ 69 44.4%
1984
ADMK+ 195 53.9%
DMK+ 34 37%
1989
DMK+ 169 37.9%
ADMK(J) 30 22.4%
INC(I) 26 19.83%
ADMK (Ja) 2 9.1%
Notice how DMK alliance's vote share increased by only 0.9% but the seats won changed drastically. Also notice how INC still had a massive 20% vote share in 1989.
1991
ADMK+ 225 59.8%
DMK+ 7 30%
Rajiv Gandhi death
1996
DMK+ 221 53.8%
ADMK+ 4 27.1%
Jayalalitha corruption. See the massive swing from previous election
2001
ADMK+ 196 50.1%
DMK+ 37 38.7%
2006
DMK+ 163 44.8%
ADMK+ 69 39.9%
DMDK Captain secured 8.4% and won a seat
2011
ADMK+ 203 51.9%
DMK+ 31 39.5%
DMK Corruption
2016
ADMK+ 40.9%
DMK+ 39.9%
This is very interesting. 2011 everyone knows how bad angi incumbency against DMK was, however in 2016 their vote share has increased only by 0.4%. Reason is Jayalalitha strategy of Fielding Makkal Nala kootani which secured 6.1% and PMK also secured 5.3% independently. That is why despite ADMK's vote share dipping by 11% they retained power. Both VCK and PMK were not aligned with either DMK or ADMK.
2021
DMK+ 159 45.4%
ADMK+ 75 39.7%
NTK got 6.58% AMMK got 2.5% and Makkal Needhi Mayyam got 2.6%
If DMK can retain this alliance and unless there is a major anti incumbency their vote share will max dip to 40%. Can ADMK rally everyone together to win? That is the major question for this election