What was the date of the poll from Survey USA that showed a lead margin smaller than 5.5?
CREATE TABLE "opinion_polling_for_the_united_states_se" (
  "poll_source" text,
  "dates_administered" text,
  "democrat_mary_landrieu" text,
  "republican_john_kennedy" text,
  "lead_margin" real
);
SELECT "dates_administered" FROM "opinion_polling_for_the_united_states_se" WHERE "lead_margin"<5.5 AND "poll_source"='survey usa';