On July 31, 2008, what are the Democrat: Vivian Davis Figures percentages?
CREATE TABLE "opinion_polling_for_the_united_states_se" (
  "poll_source" text,
  "dates_administered" text,
  "democrat_vivian_davis_figures" text,
  "republican_jeff_sessions" text,
  "lead_margin" real
);
SELECT "democrat_vivian_davis_figures" FROM "opinion_polling_for_the_united_states_se" WHERE "dates_administered"='July 31, 2008';