user: Question: Why was a seat left open fo Connecticut At-large?
Columns: ['District', 'Vacator', 'Reason for change', 'Successor', 'Date successor seated']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Pennsylvania 4th', 'John A. Hanna (DR)', 'Died July 23, 1805', 'Robert Whitehill (DR)', 'Seated November 7, 1805']
SQL:

assistant: SELECT "Reason for change" FROM "Table" WHERE "District" = 'Connecticut At-large';