CREATE TABLE people (people_id NUMBER, sex CLOB, name CLOB, date_of_birth CLOB, height NUMBER, weight NUMBER)
CREATE TABLE candidate (candidate_id NUMBER, people_id NUMBER, poll_source CLOB, date CLOB, support_rate NUMBER, consider_rate NUMBER, oppose_rate NUMBER, unsure_rate NUMBER)

Which poll resource provided the most number of candidate information?
SELECT poll_source FROM candidate GROUP BY poll_source ORDER BY COUNT(*) DESC LIMIT 1
SELECT "poll_source" FROM "candidate" GROUP BY "poll_source" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY