user: Question: How many districts have Bart Stupak as the incumbent?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Results', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Michigan 1', 'Bart Stupak', 'Democratic', 1992.0, 'Re-elected', 'Bart Stupak (D) 59% Chuck Yob (R) 41%']
SQL:

assistant: SELECT COUNT("District") FROM "Table" WHERE "Incumbent" = 'Bart Stupak';