What was the lead margin when Nixon had 48% and reporting was done by Rasmussen Reports?
CREATE TABLE "opinion_polling_for_the_united_states_gu" (
  "poll_source" text,
  "dates_administered" text,
  "democrat_jay_nixon" text,
  "republican_kenny_hulshof" text,
  "lead_margin" real
);
SELECT COUNT("lead_margin") FROM "opinion_polling_for_the_united_states_gu" WHERE "democrat_jay_nixon"='48%' AND "poll_source"='rasmussen reports';