CREATE TABLE "united_states_house_of_representatives_e" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "result" text,
  "candidates" text
);

Question: Name the number of incumbents for texas 12 
SQL: SELECT COUNT("incumbent") FROM "united_states_house_of_representatives_e" WHERE "district"='Texas 12';