Nearly on one out of two occasions, DMK, AIADMK retain seats they win in bypolls

It can be called a case of 50:50. Almost on one out of two occasions since 2006, the party that wins an Assembly byelection has successfully defended the seat in the subsequent general election to the Assembly.

Perhaps, this aspect of the recent history of byelections in the State triggers the two principal players — the DMK and the AIADMK — to approach any byelection with a high degree of intensity, as seen recently in Erode (East).

Only one out of 44 Assembly byelections since 2006 saw a margin of victory exceeding one lakh votes

In the last 17-odd years, there were 44 byelections, of which Tiruparankundram had byelections twice during the term of the 15th Assembly (2016-21). One constituency, Ilayangudi, was merged with Manamadurai during the 2008 delimitation exercise. Effectively, the number of byelections considered has gone down to 42.

In the period starting 2006, Dr. Radhakrishnan Nagar, too, witnessed two byelections but during the lifetime of different Houses — one in the 14th Assembly and another in the 15th.

Of the effective number of 42, the DMK-led front and the AIADMK retained 22 seats with the ruling party accounting for 13 and the latter eight.

The road to Erode (East)

The remaining seat, Thiruporur, went in favour of the VCK, an ally of the DMK, during the 2021 Assembly election. But for two seats (Tiruchendur and Cumbum), the remaining 12 seats defended successfully by the DMK-led coalition were all won in April-May 2019, when the Assembly byelections took place for 22 constituencies.

Tiruchendur and Cumbum, which had bypolls in August 2009, remained in the possession of the DMK in the 2011 Assembly election too.

In the 2021 Assembly election, the AIADMK was able to retain only four (Pappireddipatti, Harur, Sulur and Nilakottai) of the nine constituencies where it won in 2019.

The organisation retained, during the 2016 election, three other constituencies (Sankarankoil, Yercaud and Srirangam) where it won in the byelections during 2012-15.

Of the 20 seats that went to different parties in the subsequent general elections, the AIADMK lost 10 seats, while the DMK-led combine could not retain nine. The Independent — AMMK founder T.T.V. Dhinakaran — accounted for the lone seat. Among the seats that the principal Opposition party lost in 2021 were Manamadurai and Sattur, once regarded as strongholds.

Thiruparankundram and Pennagaram were the two constituencies that the DMK won in 2019 and 2010 byelections, but it suffered defeat in these seats in the 2021 and 2011 general elections.

The contrast in the voting behaviour between a by-election and the general election could be seen in Dr. Radhakrishnan Nagar, where former Chief Minister Jayalalithaa won by 1.5 lakh votes in the 2015 by-election. The next year, her margin went down to less than 40,000 votes. An important factor was that the DMK did not field its nominee in R.K. Nagar in 2015.