Who was the democratic incumbent in the Illinois 11 district who was re-elected? 
CREATE TABLE "table1_1341707_15" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" text,
  "result" text,
  "candidates" text
);
SELECT "incumbent" FROM "table1_1341707_15" WHERE "party"='Democratic' AND "result"='Re-elected' AND "district"='Illinois 11';