CREATE TABLE table_18421 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

What candidates were in the election when a republican was re-elected?
SELECT "Candidates" FROM table_18421 WHERE "Result" = 'Re-elected' AND "Party" = 'Republican'
SELECT "Candidates" FROM "table_18421" WHERE "Party" = 'Republican' AND "Result" = 'Re-elected'