CREATE TABLE table_15144 ("Electorate" TEXT, "Incumbent" TEXT, "Winner" TEXT, "Majority" FLOAT, "Runner up" TEXT)

Who was the incumbent when Arthur Osborne won the election?
SELECT "Incumbent" FROM table_15144 WHERE "Winner" = 'arthur osborne'
SELECT "Incumbent" FROM "table_15144" WHERE "Winner" = 'arthur osborne'