CREATE TABLE table_44623 ("Poll Source" TEXT, "Sample Size" FLOAT, "Margin of Error" FLOAT, "Date" TEXT, "Democrat" TEXT, "Republican" TEXT)

What was the sample size for polling on May 2-7, 2007 for Hillary Clinton?
SELECT "Sample Size" FROM table_44623 WHERE "Date" = 'may 2-7, 2007' AND "Democrat" = 'hillary clinton'
SELECT "Sample Size" FROM "table_44623" WHERE "Date" = 'may 2-7, 2007' AND "Democrat" = 'hillary clinton'