What was McCain's percentage when Obama had 64.39% of the vote?
CREATE TABLE "by" (
  "parish" text,
  "obamapct" text,
  "obamanum" real,
  "mc_cainpct" text,
  "mc_cainnum" real
);
SELECT "mc_cainpct" FROM "by" WHERE "obamapct"='64.39%';