What percentage of the votes did Obama get in the county where McCain got 3648 votes?
CREATE TABLE "by_county" (
  "county" text,
  "obamapct" text,
  "obamanum" real,
  "mc_cainpct" text,
  "mc_cainnum" real,
  "total" real
);
SELECT "obamapct" FROM "by_county" WHERE "mc_cainnum"=3648;