On what date was the poll showing John Kennedy with 45% and Mary Landrieu with 38%?
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 "republican_john_kennedy"='45%' AND "democrat_mary_landrieu"='38%';