Police said Arumugam and his supporters were waylaid by the gang in three cars and attacked with sickles and iron rods, leaving them seriously injured.
They have been hospitalised and their condition is stated to be serious.
Police said seven persons, suspected to be activists of Tamizhar Vazhvuirmai Katchi, have been arrested and cases registered against 50 others.
The incident triggered tension in various parts of the district today. Shops in Kunnanchavadi remained closed to protest against the attack.
Police suspect the attack could be linked to the bomb attack on the car of a dalit leader recently near Villipuram.