user: Question: How many different pairs of candidates were there for the district first elected in 1988?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Florida 4', 'Ander Crenshaw', 'Republican', 2000.0, 'Re-elected', 'Ander Crenshaw (R) 77.2% Troy Stanley (I) 22.8%']
SQL:

assistant: SELECT COUNT("Candidates") FROM "Table" WHERE "First elected" = 1988.0;