CREATE TABLE table_18191 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Result" TEXT, "Candidates" TEXT)

what's the total number of candidates for first elected in 1948 , 1964
SELECT COUNT("Candidates") FROM table_18191 WHERE "First elected" = '1948 , 1964'
SELECT COUNT("Candidates") FROM "table_18191" WHERE "First elected" = '1948 , 1964'