user: Question: Name the number of incumbents for Texas 12 
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Texas 1', 'Wright Patman', 'Democratic', 1928.0, 'Re-elected', 'Wright Patman (D) 94.7% Thomas A. Clarke (R) 5.3%']
SQL:

assistant: SELECT COUNT("Incumbent") FROM "Table" WHERE "District" = 'Texas 12';