user: Question: Who was the runner up for the Nagapattinam constituency?
Columns: ['Constituency', 'Winner', 'Party', 'Margin', 'Runner-up a', 'Party a']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Madras North', 'Krishnan Manoharan', 'DMK', 61334.0, 'S. C. C. A. Pillai', 'INC']
SQL:

assistant: SELECT "Runner-up a" FROM "Table" WHERE "Constituency" = 'Nagapattinam';