What is the percentage for Mel Martinez when the sample size is 800?
CREATE TABLE "polling" (
  "poll_source" text,
  "date_s_administered" text,
  "sample_size" real,
  "margin_of_error" text,
  "mel_martinez_r" text,
  "betty_castor_d" text
);
SELECT "mel_martinez_r" FROM "polling" WHERE "sample_size"=800;