How many incumbents was first elected in the Anti-Masonic party?
CREATE TABLE "table1_2668173_4" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "result" text,
  "candidates" text
);
SELECT COUNT("first_elected") FROM "table1_2668173_4" WHERE "party"='Anti-Masonic';