The door of the house and some part of the front portion suffered damage and glass splinters were seen strewn on the spot, police said.
District Superintendent of Police M Durai visited the house, now occupied by the family of Raja's brother, this morning and held an on-the-spot investigation into the incident that occurred around midnight last night.
The duo had come riding a two-wheeler and fled the spot after throwing the petrol bomb, the SP said, adding, CCTV recordings in the street showed a motorbike passing through it. DSP Muthamizh and Karaikudi North Inspector Pitchaipandian had visited the spot soon after the incident.
Police said they arrested 42 members of BJP and Hindu Munnani for staging a road block in the town demanding the arrest of those responsible for the attack.
Armed Police picket had been posted at the house, police said. Raja has received murder threats twice in the past two years. In 2013, a two-member gang had gone to a garden owned by Raja and threatened the security and told him that they would kill Raja.
Last year, two persons had dropped a letter threatening that Raja would be murdered in the house. Police were confident of nabbing the culprits, the SP said.