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