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

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%'