CREATE TABLE table_23812 ("Date of opinion poll" TEXT, "Conductor" TEXT, "Sample size" FLOAT, "For" TEXT, "Against" TEXT, "Undecided" TEXT)

Who conducted the poll with sample size of 2000 that shows 18% undecided?
SELECT "Conductor" FROM table_23812 WHERE "Undecided" = '18%' AND "Sample size" = '2000'
SELECT "Conductor" FROM "table_23812" WHERE "Sample size" = '2000' AND "Undecided" = '18%'