Who were the running candidates when Samuel Riker was the incumbent?
CREATE TABLE "table1_2668374_10" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "result" text,
  "candidates" text
);
SELECT "candidates" FROM "table1_2668374_10" WHERE "incumbent"='Samuel Riker';