What was Democrat: Tom Harkin's percentage when the poll source was Rasmussen Reports and the lead margin was 14?
CREATE TABLE "opinion_polling_for_the_united_states_se" (
  "poll_source" text,
  "dates_administered" text,
  "democrat_tom_harkin" text,
  "republican_christopher_reed" text,
  "lead_margin" real
);
SELECT "democrat_tom_harkin" FROM "opinion_polling_for_the_united_states_se" WHERE "poll_source"='rasmussen reports' AND "lead_margin"=14;