user: Question: what's the total number of candidates for first elected in 1948 , 1964
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Illinois 9', 'Sidney Yates', 'Democratic', '1948 , 1964', 'Re-elected', 'Sidney Yates (D) 63.40% Joseph Walsh (R) 36.60%']
SQL:

assistant: SELECT COUNT("Candidates") FROM "Table" WHERE "First elected" = '1948 , 1964';