user: Question: When was the first elected when the party was Republican and the candidate were Robert H. Michel (R) 66.1% Rosa Lee Fox (D) 33.9%?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Illinois 2', 'Abner J. Mikva', 'Democratic', 1968.0, 'Re-elected', 'Abner J. Mikva (D) 74.7% Harold E. Marks (R) 25.3%']
SQL:

assistant: SELECT "First elected" FROM "Table" WHERE "Party" = 'Republican' AND "Candidates" = 'Robert H. Michel (R) 66.1% Rosa Lee Fox (D) 33.9%';