What is the lowest population in which 28.0% are democrat?
CREATE TABLE "table1_27003223_4" (
  "city" text,
  "population" real,
  "registered_voters" text,
  "democratic" text,
  "republican" text,
  "d_r_spread" text,
  "other" text,
  "no_party_preference" text
);
SELECT MIN("population") FROM "table1_27003223_4" WHERE "democratic"='28.0%';