What is McCains percent when Obamas is 39.13%
CREATE TABLE "by_county" (
  "county" text,
  "obamapct" text,
  "obamanum" real,
  "mc_cainpct" text,
  "mc_cainnum" real
);
SELECT COUNT("mc_cainnum") FROM "by_county" WHERE "obamapct"='39.13%';