CREATE TABLE table_18529 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

How many candidates ran against barratt o'hara?
SELECT COUNT("Candidates") FROM table_18529 WHERE "Incumbent" = 'Barratt O''Hara'
SELECT COUNT("Candidates") FROM "table_18529" WHERE "Incumbent" = 'Barratt O\'Hara'