CREATE TABLE table_61920 ("Rank:" FLOAT, "Prime Minister:" TEXT, "Party:" TEXT, "Assumed Office:" TEXT, "Left Office:" TEXT, "TOTAL Time in Office:" TEXT)

What is the party of the prime minister who left office on 11 March 1983?
SELECT "Party:" FROM table_61920 WHERE "Left Office:" = '11 march 1983'
SELECT "Party:" FROM "table_61920" WHERE "Left Office:" = '11 march 1983'