Since there is no official divisions of regions and different media houses have their own, I have made my own divisions and subdivisions. Here's what it looks like.
Chennai : Essentially comprising just Chennai district. Most other divisions keep it as 16 seats, but my guess is that the politics spills over into the entire district and not just the metropolitan area.
The other regions are described in more detail in the following posts.
[1/n]
Delta : the lower Kaveri basin and the Kaveri delta. In most divisions this region is bigger. I have removed Cuddalore and Pudukottai from this region as I felt their politics was more similar to their other neighboring regions.
Western Chola - Tiruchirapalli, Ariyalur and Perambalur
Central Chola - Thanjavur and Tiruvarur
Coastal Chola - Mayiladuthurai and Nagapattinam
Though delta politics is quite homogeneous, I made the divisions because I suspect there may be a change in 2026.
[4/n]
Raboniel Shadowsong