CREATE TABLE table_45523 ("Poll Source" TEXT, "Dates administered" TEXT, "Democrat: Tom Harkin" TEXT, "Republican: Christopher Reed" TEXT, "Lead Margin" FLOAT)

What were the dates administered when the lead margin was larger than 14 and the poll source was Research 2000?
SELECT "Dates administered" FROM table_45523 WHERE "Lead Margin" > '14' AND "Poll Source" = 'research 2000'
SELECT "Dates administered" FROM "table_45523" WHERE "Lead Margin" > '14' AND "Poll Source" = 'research 2000'