CREATE TABLE table_26257 ("Party" TEXT, "Result ,  Parliam. election 2005" TEXT, "Result ,  County elections 2007" TEXT, "Aug 2008" TEXT, "Sep 2008" TEXT, "Oct 2008" TEXT, "Nov 2008" TEXT, "Dec 2008" TEXT, "Jan 2009" TEXT, "Feb 2009" TEXT, "Mar 2009" TEXT, "Apr 2009" TEXT, "May 2009" TEXT, "Jun 2009" TEXT, "Jul 2009" TEXT, "Aug 2009" TEXT)

What was the polling average in Aug 2009 when is was 5.0% in Sep 2009?
SELECT "Aug 2008" FROM table_26257 WHERE "Sep 2008" = '5.0%'
SELECT "Aug 2008" FROM "table_26257" WHERE "Sep 2008" = '5.0%'