What is the percentage for Schweitzer when the lead margin is 29?
CREATE TABLE "opinion_polling_for_the_united_states_gu" (
  "poll_source" text,
  "dates_administered" text,
  "democrat_brian_schweitzer" text,
  "republican_roy_brown" text,
  "libertarian_stan_jones" text,
  "lead_margin" real
);
SELECT "democrat_brian_schweitzer" FROM "opinion_polling_for_the_united_states_gu" WHERE "lead_margin"=29;