The first ripples of the Congress’s political realignment in Tamil Nadu were felt on Friday as the DMK wrote to Lok Sabha Speaker Om Birla, seeking a change in the seating arrangement of its MPs, saying it would not be appropriate for its members to sit alongside those of the Congress. A founding member of the INDIA bloc, the DMK was the Congress’s dependable and steadfast ally in the fractious alliance so far. The bitter Congress-DMK split will cast a shadow on the INDIA bloc’s cohesion and coordination in Parliament. The DMK’s move did not come as a surprise given the manner in which it attacked the Congress for dumping it unceremoniously and joining hands with Vijay’s TVK , not just for the formation of the state government but for all future elections, too. Although the Congress would be relieved by the fact that the other DMK allies — the CPI and CPI(M) — have decided to back the TVK, some within the party believe its leadership of the INDIA bloc would soon come under question.…