user: Question: what's party with result being Retired to run for U. S. Senate Republican hold
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Florida 3', 'Charles Edward Bennett', 'Democratic', 1948.0, 'Re-elected', 'Charles Edward Bennett (D) Unopposed']
SQL:

assistant: SELECT "Party" FROM "Table" WHERE "Result" = 'Retired to run for U. S. Senate Republican hold';