SELECT "Polling institute" FROM table_66677 WHERE "Lead" = '6%'
Which polling institute showed a lead of 6%?
CREATE TABLE table_66677 (
    "Date(s) Released" text,
    "Polling institute" text,
    "Nationalist" text,
    "Labour" text,
    "Democratic Alternative" text,
    "Undecided/ No answer" text,
    "Lead" text
)