CREATE TABLE table_203_615 (id DECIMAL, "district" TEXT, "incumbent" TEXT, "party" TEXT, "first\ elected" DECIMAL, "result" TEXT, "candidates" TEXT)

which party had the most candidates , republican or democratic ?
SELECT "party" FROM table_203_615 WHERE "party" IN ('republican', 'democratic') GROUP BY "party" ORDER BY COUNT(*) DESC LIMIT 1
SELECT "party" FROM "table_203_615" WHERE "party" IN ('republican', 'democratic') GROUP BY "party" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1