CREATE TABLE table_18517 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

How many parties match the canididates listed as howard baker, sr. (r) 68.9% boyd w. cox (d) 31.1%?
SELECT COUNT("Party") FROM table_18517 WHERE "Candidates" = 'Howard Baker, Sr. (R) 68.9% Boyd W. Cox (D) 31.1%'
SELECT COUNT("Party") FROM "table_18517" WHERE "Candidates" = 'Howard Baker, Sr. (R) 68.9% Boyd W. Cox (D) 31.1%'