user: Question: Name the most margin for NCO party and P. Ramachandran won
Columns: ['Constituency', 'Winner', 'Party', 'Margin', 'Runner-up a', 'Party a']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Madras North', 'A. V. P. Asaithambi', 'DMK', 45103.0, 'K. Manoharan', 'ADMK']
SQL:

assistant: SELECT MAX("Margin") FROM "Table" WHERE "Party" = 'NCO' AND "Winner" = 'P. Ramachandran';