CREATE TABLE table_43584 ("Poll Source" TEXT, "Dates administered" TEXT, "Democrat: Mary Landrieu" TEXT, "Republican: John Kennedy" TEXT, "Lead Margin" FLOAT)

On what date was the poll showing John Kennedy with 45% and Mary Landrieu with 38%?
SELECT "Dates administered" FROM table_43584 WHERE "Republican: John Kennedy" = '45%' AND "Democrat: Mary Landrieu" = '38%'
SELECT "Dates administered" FROM "table_43584" WHERE "Democrat: Mary Landrieu" = '38%' AND "Republican: John Kennedy" = '45%'