CREATE TABLE table_43587 ("Poll Source" TEXT, "Dates administered" TEXT, "Democrat: Mary Landrieu" TEXT, "Republican: John Kennedy" TEXT, "Lead Margin" FLOAT)

Which poll shows Democrat Mary Landrieu with 53% against Republican John Kennedy?
SELECT "Republican: John Kennedy" FROM table_43587 WHERE "Democrat: Mary Landrieu" = '53%'
SELECT "Republican: John Kennedy" FROM "table_43587" WHERE "Democrat: Mary Landrieu" = '53%'