- TTV Dhinakaran, sidelined by the AIADMK, contesting as an Independent
- AIADMK, DMK had expressed confidence that they would win
- A record 77% voter turnout was recorded in the RK Nagar by-election
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TTV Dhinakaran had polled 89,013 votes in comparison to E Madhusudanan, the veteran AIADMK candidate's 48,306 votes. The victory of the 54-year-old, who tried to get E Palaniswami removed from the Chief Minister's post, is seen as a huge psychological setback for the ruling AIADMK.
This was the first time in 18 years that a ruling party in the state lost a by-election. The AIADMK blamed the loss on a "secret pact" between the Mr Dhinakaran and the opposition DMK and accused them of bribing voters.
Even before the victory announcement, an AIADMK parliamentarian visited Mr Dhinakaran, fuelling speculation that many lawmakers of the Palaniswami camp were contemplating switching sides.
Marudhu Ganesh, the candidate of the opposition DMK was a distant third with 24,681 votes and lost his deposit for failing to get one-sixth of the total votes cast. His performance is seen as a downer for DMK leader MK Stalin, who has been trying to project himself as an effective second to his father M Karunanidhi.
The victory is seen as a vindication for Mr Dhinakaran, who had been arrested for allegedly bribing Election Commission officials to get the "two-leaves" symbol of the AIADMK, and subsequently sidelined by the AIADMK after the two warring factions of the party, led by E Palaniswami and O Panneerselvam, patched up.
Earlier this month, he also lost the AIADMK's two-leaves election symbol after the Election Commission recognised the merged AIADMK as the "real" party. He had contested with a pressure cooker as his election symbol.
Mr Dhinakaran, who is currently out on bail, has denied the bribery allegations. His arrest is seen by his supporters as an effort by the BJP-led central government to give a boost to the AIADMK. The BJP, which has a marginal presence in Tamil Nadu, has been trying to expand its footprint in the state and a tie-up with the AIADMK is seen as an option for the party.
The RK Nagar set in Chennai had been left vacant after the death of Jayalalithaa in December 2016. In April, the by-elections to choose a new lawmaker were postponed over allegations that the AIADMK paid Rs 89 crore to voters to buy support for Mr Dhinakaran, who was the party's candidate at the time.
A record 77 per cent voter turnout was recorded in the by-election that was finally held on Thursday in the shadow of another round of cash-for-votes allegations. The election officials, who had refused to postpone the polls again, said the polling figure was the highest since 2011.
The split in the AIADMK came after VK Sasikala, the now-jailed longtime companion of Jayalalithaa, made a bid to capture the top job in the state from O Panneerselvam, the regular stand-in for the former Chief Minister. The opposing factions merged in August. Ms Sasikala and Mr Dhinakaran got evicted from the party as part of a pre-merger deal. They have challenged that decision.