Question: 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 "2-18506586-1" WHERE "Political party" = 'Conservative' AND "Constituency" = 'South West Devon' AND "Conservative" > 2.0 AND "Name" = 'Plymstock Radford';