CREATE TABLE table_21795 ("Poll Source" TEXT, "Dates administered" TEXT, "Democrat: Jay Nixon" TEXT, "Republican: Kenny Hulshof" TEXT, "Lead Margin" TEXT)

How many different lead margins were stated in the poll administered on September 11, 2008?
SELECT COUNT("Lead Margin") FROM table_21795 WHERE "Dates administered" = 'September 11, 2008'
SELECT COUNT("Lead Margin") FROM "table_21795" WHERE "Dates administered" = 'September 11, 2008'