CREATE TABLE table_18229 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

Who are all the candidates who ran in the district where Ralph Regula is the incumbent?
SELECT "Candidates" FROM table_18229 WHERE "Incumbent" = 'Ralph Regula'
SELECT "Candidates" FROM "table_18229" WHERE "Incumbent" = 'Ralph Regula'