user: Question: What was the sample size for polling on May 2-7, 2007 for Hillary Clinton?
Columns: ['Poll Source', 'Sample Size', 'Margin of Error', 'Date', 'Democrat', 'Republican']
Types: ['text', 'real', 'real', 'text', 'text', 'text']
Sample row: ['Quinnipiac', 1697.0, 2.4, 'Mar 19-24, 2008', 'Hillary Clinton', 'John McCain']
SQL:

assistant: SELECT "Sample Size" FROM "Table" WHERE "Date" = 'May 2-7, 2007' AND "Democrat" = 'Hillary Clinton';