user: Question: How many different lead margins were stated in the poll administered on September 11, 2008?
Columns: ['Poll Source', 'Dates administered', 'Democrat: Jay Nixon', 'Republican: Kenny Hulshof', 'Lead Margin']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Public Policy Polling', 'November 2, 2008', '57.9%', '38.4%', '19.5']
SQL:

assistant: SELECT COUNT("Lead Margin") FROM "Table" WHERE "Dates administered" = 'September 11, 2008';