CREATE TABLE table_23810 ("Date of opinion poll" TEXT, "Conductor" TEXT, "Sample size" FLOAT, "For" TEXT, "Against" TEXT, "Undecided" TEXT)

How many polls taken on different dates show an undecided percentage of 25%?
SELECT COUNT("Date of opinion poll") FROM table_23810 WHERE "Undecided" = '25%'
SELECT COUNT("Date of opinion poll") FROM "table_23810" WHERE "Undecided" = '25%'