CREATE TABLE table_name_57 (electorate INTEGER, name VARCHAR(255), political_party VARCHAR(255), constituency VARCHAR(255))
What is the smallest electorate for the Conservative party in South West Devon constituency, with over 2 conservatives and a name of Plymstock Radford?
    
SQL: SELECT MIN(electorate) FROM table_name_57 WHERE political_party = "conservative" AND constituency = "south west devon" AND "conservative" > 2 AND name = "plymstock radford"