user: Question: Which poll source has a lead of 17?
Columns: ['Poll Source', 'Dates administered', 'Democrat: Dick Durbin', 'Republican: Steve Sauerberg', 'Lead Margin']
Types: ['text', 'text', 'text', 'text', 'real']
Sample row: ['Rasmussen Reports', 'October 13, 2008', '62%', '31%', 31.0]
SQL:

assistant: SELECT "Poll Source" FROM "Table" WHERE "Lead Margin" = 17.0;