CREATE TABLE table_28855 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Result" TEXT, "Candidates" TEXT)

Who were the candidates in districk Pennsylvania 12?
SELECT "Candidates" FROM table_28855 WHERE "District" = 'Pennsylvania 12'
SELECT "Candidates" FROM "table_28855" WHERE "District" = 'Pennsylvania 12'