CREATE TABLE table_2668336_19 (incumbent VARCHAR(255), candidates VARCHAR(255), result VARCHAR(255))
Who were the incumbent(s) in the election featuring  john murray (dr) 50.4% george denison (dr) 49.6% with a result of a retired democratic-republican hold?
    
SQL: SELECT incumbent FROM table_2668336_19 WHERE candidates = "John Murray (DR) 50.4% George Denison (DR) 49.6%" AND result = "Retired Democratic-Republican hold"