CREATE TABLE table_18160 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Results" TEXT, "Candidates" TEXT)

How many candidates ran in the election where Mike Doyle was the incumbent?
SELECT COUNT("Candidates") FROM table_18160 WHERE "Incumbent" = 'Mike Doyle'
SELECT COUNT("Candidates") FROM "table_18160" WHERE "Incumbent" = 'Mike Doyle'