user: Question: What is the date that the polls were going on at Quinnipiac when John McCain was the republican, Barack Obama was the democrat and the sample size was bigger than 1427?
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 "Date" FROM "Table" WHERE "Republican" = 'John McCain' AND "Poll Source" = 'Quinnipiac' AND "Democrat" = 'Barack Obama' AND "Sample Size" > 1427.0;