The issue has kept the DMK and DMDK on tenterhooks, which are locked in a fierce battle for the sixth seat in the polls.
Without going into the specifics, highly placed sources in the party said a decision in this regard will be taken tomorrow.
With Lok Sabha elections not far away, the party high command is weighing on whom its five MLAs in the Legislative Assembly will support, DMK or DMDK.
AIADMK and Left parties, which have fielded four and one candidate respectively, have one have enough numbers to ensure victory of their respective contestants. The ruling party is backing CPI nominee D Raja.
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Congress had contested last Lok Sabha polls in alliance with the DMK, its ally for the past nine years in the UPA which had parted ways a few months back.
The election is a matter of prestige for DMK supremo M Karunanidhi who has fielded his daughter Kanimozhi.
Baalu, who is the DMK's parliamentary party leader, met Defence Minister and Congress troubleshooter A K Antony at South Block here yesterday and reminded him about the letter written by Karunanidhi to party president Sonia Gandhi seeking support for Kanimozhi.
DMK has bagged the support of Puthiya Tamizhagam and Manitha Neya Makkal Katchi, both having two MLAs each.