CREATE TABLE table_18133 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Results" CLOB, "Candidates" CLOB)

Who ran in the district elections won by Tom Petri?
SELECT "Candidates" FROM table_18133 WHERE "Incumbent" = 'Tom Petri'
SELECT "Candidates" FROM "table_18133" WHERE "Incumbent" = 'Tom Petri'