By 1998, when Lok Sabha went for a mid-term poll thereby breaking the simultaneous poll schedule that Tamil Nadu Assembly shared with the Lok Sabha, the regional players had emerged strong. In the two decades since then, the national parties have had even lesser presence in both Parliament and Assembly elections, reflecting their vote share that had plummeted after staying away from state power for decades. 

It was DMK president M Karunanidhi who first developed this seat-sharing strategy in 1971 where the regional ally cornered a lion’s share of Assembly seats – and thus kept the national party away from power even before the state went for poll. 

When former prime minister Indira Gandhi broke away from the Congress to form the Congress (Indira), Karunanidhi allocated nine Parliament constituencies to her party. But the DMK refused to give any seat to the new party on the ground that it was yet to establish itself in Tamil Nadu. The DMK contested from 203 Assembly seats and won 184, a record that stands till date.

Barring 1980 when Congress (I) contested from 114 Assembly seats, the national parties did not make a hard bargain for more Assembly seats in the elections till 1996.

In 1984, when MGR was battling for life in the United States, the AIADMK evolved a 1:2 formula: two-third Assembly seats to the regional party and a similar share to the national party in Parliament seats. Despite riding a sympathy wave after Indira Gandhi’s assassination, Congress contested from just 73 Assembly seats compared to its regional ally’s share of 155. The Congress had its best chance of capturing power in Tamil Nadu in 1991, when former Prime Minister Rajiv Gandhi was assassinated in Sriperumbudur, resulting in a massive sympathy wave. However, it had already settled for the seat-sharing formula with AIADMK under Jayalalithaa by then, which won a massive mandate with 164 seats. Congress accepted a similar formula in the next elections in 1996, the last time polls were held simultaneously. 

Since then, Tamil Nadu has had separate elections. But by this time, the regional players had grown too stronger and dictated the bargain. With its strength depleted after GK Moopanar went out and formed TMC, Congress contested only from 14 seats in 2001, while BJP got 21 seats in DMK front. Five years later, despite the merger of TMC, it got only 48 seats in the Assembly polls from the DMK. 

In 2011 Assembly polls, it did manage to prise out 63 seats from DMK – which was hit by the 2G scam – but the alliance was routed. In the last elections in 2016, the party was given just 41 seats and won a meagre eight.