How many different results were there for the number of votes fro Obama in the county where he got 27.8% of the votes?
CREATE TABLE "by_county" (
  "county" text,
  "obamapct" text,
  "obamanum" real,
  "mc_cainpct" text,
  "mc_cainnum" real,
  "total" real
);
SELECT COUNT("obamanum") FROM "by_county" WHERE "obamapct"='27.8%';