How many polls taken on different dates show an undecided percentage of 25%?
CREATE TABLE "opinion_polls" (
  "date_of_opinion_poll" text,
  "conductor" text,
  "sample_size" real,
  "for" text,
  "against" text,
  "undecided" text
);
SELECT COUNT("date_of_opinion_poll") FROM "opinion_polls" WHERE "undecided"='25%';