How many parties match the canididates listed as howard baker, sr. (r) 68.9% boyd w. cox (d) 31.1%?
CREATE TABLE "united_states_house_of_representatives_e" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "result" text,
  "candidates" text
);
SELECT COUNT("party") FROM "united_states_house_of_representatives_e" WHERE "candidates"='Howard Baker, Sr. (R) 68.9% Boyd W. Cox (D) 31.1%';