user: Question: What district first elected a Democratic incumbent in 1998?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Results', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Wisconsin 1', 'Paul Ryan', 'Republican', 1998.0, 'Re-elected', 'Paul Ryan (R) 62.8% Jeff Thomas (D) 37.2%']
SQL:

assistant: SELECT "District" FROM "Table" WHERE "Party" = 'Democratic' AND "First elected" = 1998.0;