user: Question: Who are all the candidates who ran in the district where Ralph Regula is the incumbent?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Ohio 1', 'Tom Luken', 'Democratic', 1976.0, 'Re-elected', 'Tom Luken (D) 56.5% Steve Chabot (R) 43.5%']
SQL:

assistant: SELECT "Candidates" FROM "Table" WHERE "Incumbent" = 'Ralph Regula';