What is Party, when Results is "Re-Elected", when First Elected is greater than 1990, and when District is "Minnesota 4"?
CREATE TABLE "minnesota" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "results" text
);
SELECT "party" FROM "minnesota" WHERE "results"='re-elected' AND "first_elected">1990 AND "district"='minnesota 4';