CREATE TABLE table_66677 ("Date ( s )  Released" TEXT, "Polling institute" TEXT, "Nationalist" TEXT, "Labour" TEXT, "Democratic Alternative" TEXT, "Undecided/ No answer" TEXT, "Lead" TEXT)

Which polling institute showed a lead of 6%?
SELECT "Polling institute" FROM table_66677 WHERE "Lead" = '6%'
SELECT "Polling institute" FROM "table_66677" WHERE "Lead" = '6%'