user: Question: Who was the incumbent in the 20th district?
Columns: ['District', 'Incumbent', 'Party', 'Elected', 'Status']
Types: ['text', 'text', 'text', 'real', 'text']
Sample row: ['1st', 'Marty Williams', 'Republican', 1995.0, 'Defeated in Primary']
SQL:

assistant: SELECT "Incumbent" FROM "Table" WHERE "District" = '20th';